IPAC2018 - List of Keywords (plasma)

Paper	Title	Other Keywords	Page
MOZGBE1	Development of Gas Stripper at RIBF	acceleration, target, electron, heavy-ion	41
	H. Imao RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan
	Charge strippers are almost inevitable for accelerations in heavy-ion accelerator complex. The fixed solid strip-pers including carbon-foil strippers are difficult to be used in on-going or upcoming new-generation in-flight RI beam facilities, e.g., RIBF (RIKEN, Japan), FAIR (GSI, Germany), FRIB (NSCL/MSU, US), HIAF (IMP, China) and RAON (RISP, Korea). The He gas stripper developed at RIBF is the first successful stripper significantly be-yond the applicable limit of the fixed carbon-foil strip-pers. We discuss the development of the gas strippers at RIBF and overview the related new-generation strippers being developed in the world.
	Slides MOZGBE1 [11.797 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBE1
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TUXGBE1	Status and Prospects for the AWAKE Experiment	electron, proton, wakefield, experiment	595
	M. Turner CERN, Geneva, Switzerland
	The AWAKE Collaboration is pursuing a demonstration of proton-driven plasma wakefield acceleration of electrons. The AWAKE experiment uses a §I{400}{GeV/c} proton bunch from the CERN SPS, with a rms bunch length of 6-§I{15}{cm}, to drive wakefields in a §I10{m} long rubidium plasma with an electron density of 10¹⁴-10¹⁵cm^-3. Since the drive bunch length is much longer than the plasma wavelength (λ_pe<§I{3}{mm}) for these plasma densities, AWAKE performed experiments to prove that the long proton bunch self-modulates in the plasma (2017). The next step is to demonstrate acceleration of electrons in the wakefields driven by the self-modulated bunch (2018). We summarize the concept of the self-modulation measurements and describe the plans and challenges for the electron acceleration experiments.
	Slides TUXGBE1 [8.878 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE1
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TUXGBE2	Study of Ultra-High Gradient Acceleration in Carbon Nanotube Arrays	electron, acceleration, wakefield, experiment	599
	J. Resta-López, A.S. Alexandrova, V. Rodin, Y. Wei, C.P. Welsch, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom Y. M. Li, Y. Zhao UMAN, Manchester, United Kingdom
	Solid-state based wakefield acceleration of charged particles was previously proposed to obtain extremely high gradients on the order of 1 − 10 TeV/m. In recent years the possibility of using either metallic or carbon nanotube structures is attracting new attention. The use of carbon nanotubes would allow us to accelerate and channel particles overcoming many of the limitations of using natural crystals, e.g. channeling aperture restrictions and thermal-mechanical robustness issues. In this paper, we propose a potential proof of concept experiment using carbon nanotube arrays, assuming the beam parameters and conditions of accelerator facilities already available, such as CLEAR at CERN and CLARA at Daresbury. The acceleration performance of carbon nanotube arrays is investigated by using a 2D Particle-In-Cell (PIC) model based on a multi-hollow plasma. Optimum experimental beam parameters and system layout are discussed.
	Slides TUXGBE2 [27.290 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE2
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TUXGBE3	Status of Plasma-Based Experiments at the SPARC_LAB Test Facility	electron, experiment, focusing, emittance	603
	E. Chiadroni, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F.G. Bisesto, E. Brentegani, F. Cardelli, G. Costa, M. Croia, D. Di Giovenale, G. Di Pirro, M. Ferrario, F. Filippi, A. Gallo, A. Giribono, A. Marocchino, L. Piersanti, R. Pompili, S. Romeo, J. Scifo, V. Shpakov, A. Stella, C. Vaccarezza, F. Villa INFN/LNF, Frascati (Roma), Italy A. Cianchi INFN-Roma II, Roma, Italy M. Marongiu, A. Mostacci Sapienza University of Rome, Rome, Italy J.B. Rosenzweig UCLA, Los Angeles, California, USA A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy A. Zigler The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	The current activity of the SPARC LAB test-facility is focused on the realization of plasma-based acceleration experiments with the aim to provide accelerating field of the order of several GV/m while maintaining the overall quality (in terms of energy spread and emittance) of the accelerated electron bunch. The current status of such an activity is presented, together with results related to the applicability of plasmas as focusing lenses in view of a complete plasma-based focusing, accelerating and extraction system.
	Slides TUXGBE3 [10.258 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE3
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TUXGBE4	Beam Quality Limitations of Plasma-Based Accelerators	electron, laser, injection, acceleration	607
	A. Ferran Pousa, R.W. Aßmann DESY, Hamburg, Germany A. Martinez de la Ossa University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Plasma-based accelerators are a promising novel technology that could significantly reduce the size and cost of future accelerator facilities. However, the typical quality and stability of the produced beams is still inferior to the requirements of Free Electron Lasers (FELs) and other applications. We present here our recent work in understanding the limitations of this type of accelerators, particularly on the energy spread and bunch length, and possible mitigating measures for future applications, like the plasma-based FEL in the EuPRAXIA design study.
	Slides TUXGBE4 [4.905 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE4
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TUPAF039	Electron Cooling Simulation and Experimental Benchmarks at LEIR	electron, experiment, simulation, solenoid	776
	A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer CERN, Geneva, Switzerland
	A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.
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TUPAL041	Vacuum Accelerating Tube with Two Symmetrically Located Targets for Neutron Generation	electron, cathode, neutron, target	1097
	V.I. Rashchikov, A.A. Isaev, A.E. Shikanov MEPhI, Moscow, Russia
	Original neutron generator* on the base of pulse accelerating vacuum tube with two targets, symmetrically located on the both sides of deuteron source is discussed. Two immersion lenses in front of each other uses as accelerating and focusing systems. Lenses cathodes are Faraday cups with targets for neutron production on the bottom. Symmetric ring magnetic elements cover immersion lenses for correcting focusing conditions. Computer simulation allows us to choose electrodes geometry and accelerating pulse value for electron flow from ion-electron emission oscillate between the targets and provide device operate as reflective triode. Estimations of neutron flow and spatio-temporal neutron field structure are done. * Patent RF N2467526, 14.06.2011
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TUPAL042	On Possibility of Reflective Triode Uses for Thermonuclear Neutron Generation in Budker-Post Trap with Pulsed Magnetic Field	neutron, proton, electron, focusing	1100
	V.I. Rashchikov, A.N. Didenko, A.A. Isaev, K.I. Kozlovskiy, V.L. Shatokhin, A.E. Shikanov, E.D. Vovchenko MEPhI, Moscow, Russia
	Scheme for thermonuclear neutron generation in compact Budker-Post trap with barrel-shaped pulsed magnetic field produced by two symmetrically located thin coils with diameter not exceed 0.05 m is proposed. During neutron generation in the trap simultaneously forms plasma which include hydrogen nuclides with density up to 10¹³ m-3 and two pulsed counter hydrogen nuclides flows accelerated in the diodes. Diodes consist of transparent anode with the form of sphere sector symmetrically covered by the same form grounded cathode. Diodes located symmetrically in front of each other, coaxially to magnetic trap. Computer simulation shows possibility to generate up to 1010 neutrons per pulse for deuterium-tritium compound in the diode system with transverse dimension ~0.1 m, amplitude and accelerating pulse duration 5.105 V and 100 nsec. The value of magnetic induction in the center of the trap should be approximately equal to 20 T.
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TUPAL043	Simulations of the Electron Column in IOTA	electron, proton, space-charge, simulation	1103
	B.T. Freemire Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay Northern Illinois Univerity, DeKalb, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea C.S. Park Korea University Sejong Campus, Sejong, Republic of Korea G. Penn LBNL, Berkeley, California, USA V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied.
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TUPAL057	Preliminary Experiments in Caesium Delivery and Gettering on the ISIS Vespa Source	experiment, ion-source, operation, site	1144
	T. M. Sarmento, R.E. Abel, D.C. Faircloth, S.R. Lawrie, J.H. Macgregor, M. Whitehead, T. Wood STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	Caesium capture by graphite at various temperatures 20- 300°C in the VESPA ion source test stand was explored in a preliminary experiment. An accompanying experiment was set up to evaluate the control of caesium boiler delivery in the various ISIS penning sources. Results indicate Cs flux fluctuates at constant settings, which must be accounted for to interpret graphite gettering results. Future studies to identify the cause of fluctuations are considered, and a more rigorous experiment to study the use of graphite is introduced.
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TUPML014	CO2 CPA Laser Development for User Experiments in Advanced Accelerators and Radiation Sources	laser, experiment, optics, operation	1556
	M.N. Polyanskiy, M. Babzien, M.A. Palmer, I. Pogorelsky BNL, Upton, Long Island, New York, USA
	The ATF* is a National User Facility for advanced research in accelerator physics and technology. The ATF's terawatt CO2 laser is a unique scientific instrument allowing researchers to explorer new particle acceleration mechanisms and to study light/matter interaction at an order-of-magnitude longer photon wavelengths compared to the majority of other laser research facilities (λ≈10μm). Continuous development over more than two decades brought the ATF's CO2 laser to the limit of peak power achievable in a conventional gas laser MOPA configuration (in ATF's amplifier geometry this is ~0.5 TW in routine operation, and up to 2 TW in some experiments). To overcome this limit, we employ, for the first time in a gas laser, a chirped-pulse amplification (CPA) scheme. The goal of our current research and development effort is to demonstrate 3-5 TW peak power at the system output and to reliably deliver a large fraction of this power as a high-quality beam to a range of user experiments. Achieving this goal will lay the ground work for implementation of a >10 TW mid-IR laser system "BESTIA" that is currently being constructed as a part of the ATF-II project. *Accelerator Test Facility at Brookhaven National Laboratory
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TUPML015	Influence of Ionization and Beam Quality on Interaction of Tw-Peak Co2 Laser With Hydrogen Plasma	laser, simulation, electron, experiment	1560
	P. Kumar, V. Samulyak SBU, Stony Brook, USA V. Samulyak, K. Yu BNL, Upton, Long Island, New York, USA
	3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombination rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.
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TUPML017	Longitudinal Phase Space Reconstruction at FLASHForward Using a Novel Transverse Deflection Cavity, PolariX-TDS	experiment, dipole, simulation, lattice	1567
	R.T.P. D'Arcy, A. Aschikhin, P. González Caminal, V. Libov, J. Osterhoff DESY, Hamburg, Germany
	The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration (PWFA) experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams are assessed for their capability to drive a free-electron laser. The ultra short, low emittance, and low energy spread properties of bunches produced from certain PWFA injection schemes naturally lend themselves to this task. However, these bunch lengths, typically in the few femtosecond range, are difficult to temporally resolve with traditional diagnostic methods. In order to longitudinally diagnose these bunches it is necessary to utilise the properties of a transverse RF deflecting cavity operating in a high-frequency regime. It is proposed that this type of X-band transverse deflection system, styled the PolariX-TDS due to its novel variable polarisation feature, will be introduced to the FLASHForward beam line in order to perform these single-shot longitudinal phase space measurements. This paper will concern itself with the efficacy of longitudinally reconstructing PWFA-bunches expected at FLASHForward with this TDS, with a focus on the variable bunch properties expected from early commissioning of the experiment.
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TUPML021	A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator	laser, electron, undulator, quadrupole	1577
	K.A. Dewhurst, H.L. Owen UMAN, Manchester, United Kingdom E. Brunetti, D.A. Jaroszynski, S.M. Wiggins USTRAT/SUPA, Glasgow, United Kingdom B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom B.D. Muratori Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by the UK Science and Technology Facilities Council, Grant No. ST/G008248/1. The Cockcroft Beamline is to be installed at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). The beamline is designed to transport 1 GeV electrons from a laser wakefield acceleration (LWFA) source to a pair of transverse gradient undulators. The project aims to produce X-ray undulator radiation in the first phase and free-electron laser (FEL) radiation in the second phase. The total beamline will be less than 23 m long, thus the Cockcroft Beamline has the potential to be the UK's first compact X-ray FEL. Here we present the main features of the beamline design.
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TUPML022	Assessment of Transverse Instabilities in Proton Driven Hollow Plasma Wakefield Acceleration	proton, electron, wakefield, focusing	1581
	Y. M. Li, G.X. Xia, Y. Zhao UMAN, Manchester, United Kingdom S.J. Gessner CERN, Geneva, Switzerland
	Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the witness beam quality. In this paper, by means of the 2D cartesian particle-in-cell simulations, we examine the potentially detrimental effects induced by the driving beam-channel offset and initial driver tilt, and then propose and assess the solutions to these driver inaccuracy issues.
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TUPML023	Amplitude Enhancement of the Self-Modulated Plasma Wakefields	proton, wakefield, focusing, ECR	1585
	Y. M. Li, G.X. Xia, Y. Zhao UMAN, Manchester, United Kingdom K.V. Lotov, A. Sosedkin Budker INP & NSU, Novosibirsk, Russia
	Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.
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TUPML030	Optimisation of D- Ion Production in a Multicusp Ion Source	ion-source, electron, extraction, dipole	1609
	A.M. George, M.P. Dehnel, S.V. Melanson, D.E. Potkins D-Pace, Nelson, British Columbia, Canada N. Broderick University of Auckland, Auckland, New Zealand H.C. McDonald, C. Philpott BSL, Auckland, New Zealand
	D-Pace's multicusp ion source achieves high beam cur-rents for negative hydrogen ions in both the TRIUMF-licensed filament-powered ion source (~18 mA) and the University of Jyväskylä-licensed RF-powered ion source (~8 mA) [1]. It is well known that ion sources producing negative deuterium ions achieve lower beam currents compared to similar negative hydrogen ion sources and indeed we have found that negative deuterium ion beam currents in our sources are typically 1/3 that of negative hydrogen beam currents. The reasons behind this are not completely understood, but factors such as the magnetic field strength and the electron temperature are believed to play a major role and offer the potential for significant optimisation. In this paper, we look into the issues surrounding swapping of deuterium for hydrogen in our ion source by studying the properties of plasmas and extracted currents with different magnetic field strengths and gas flows.
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TUPML036	ALEGRO, the Advanced LinEar collider study GROup	collider, laser, linear-collider, acceleration	1619
	P. Muggli MPI, Muenchen, Germany B. Cros CNRS LPGP Univ Paris Sud, Orsay, France
	We briefly describe activities of ALEGRO, the Advanced LinEar collider study GROup.
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TUPML040	Status of the Transverse Diagnostics at FLASHForward	electron, laser, wakefield, diagnostics	1630
	P. Niknejadi, R.T.P. D'Arcy, A. Knetsch, V. Libov, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper DESY, Hamburg, Germany M. Kaluza, M.B. Schwab, A. Sävert, C. Wirth IOQ, Jena, Germany M. Kaluza HIJ, Jena, Germany T.J. Mehrling LBNL, Berkeley, USA C.A.J. Palmer Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	Funding: Helmholtz Institute, Bundesministerium für Bildung und Forschung, and European Union‘s Horizon 2020 research and innovation program. Density modulations in plasma caused by a high-intensity laser or a high charge density electron pulse can generate extreme acceleration fields. Acceleration of electrons in such fields may produce ultra-relativistic, quasi-monoenergetic, ultra-short electron bunches over distances orders of magnitudes shorter than in state-of-the-art radio-frequency accelerators. FLASHForward is such a beam-driven plasma wakefield accelerator (PWFA) project at DESY with the goal of producing, characterizing, and utilizing such beams. Temporal characterization of the acceleration process is of crucial importance for improving the stability and control in PWFA beams. While measurement of the transient field of the femtosecond bunch in a single shot is challenging, in recent years novel techniques with great promise have been developed . This work discusses the plans and status of the transverse diagnostics at FLASHForward. A. Aschikhin et. al., NIMA , Volume 806 (11 January 2016) pp. 175-183. A. Buck et al., Nature Physics 7, (2011) 543. *C. J. Zhang et al., Phys. Rev. Lett. 119 (2017) 064801.
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TUPML041	Two-Stage Laser-Driven Plasma Acceleration With External Injection for EuPRAXIA	electron, laser, acceleration, wakefield	1634
	E.N. Svystun, R.W. Aßmann, U. Dorda, A. Ferran Pousa, T. Heinemann, B. Marchetti, P.A. Walker, M.K. Weikum, J. Zhu DESY, Hamburg, Germany A. Ferran Pousa, T. Heinemann, A. Martinez de la Ossa University of Hamburg, Hamburg, Germany T. Heinemann USTRAT/SUPA, Glasgow, United Kingdom
	The EuPRAXIA (European Particle Research Accelerator with eXcellence In Applications) project aims at producing a conceptual design for the worldwide plasma-based accelerator facility, capable of delivering multi-GeV electron beams with high quality. This accelerator facility will be used for various user applications such as compact X-ray sources for medical imaging and high-energy physics detector tests. EuPRAXIA explores different approaches to plasma acceleration techniques. Laser-driven plasma wakefield acceleration with external injection of an RF-generated electron beam is one of the basic research directions of EuPRAXIA. We present studies of electron beam acceleration to GeV energies by a two-stage laser wakefield acceleration with external injection from an RF accelerator. Electron beam injection, acceleration and extraction from the plasma, using particle-in-cell simulations, are investigated.
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TUPML042	Accurate Modeling of the Hose Instability in Plasma Based Accelerators	electron, damping, simulation, wakefield	1638
	T.J. Mehrling, C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder LBNL, Berkeley, USA
	Funding: US Department of Energy Contract No. DE-AC02-05CH11231 The hose instability is a long standing challenge for plasma-based accelerators. It is seeded by initial transverse asymmetries of the beam or plasma phase space distributions. The beam centroid displacement is thereby amplified during the propagation in the plasma, which can lead to an unstable acceleration process. A witness beam can itself cause hosing and/or may be affected by the hosing of the drive beam. The accurate study of hosing including a witness beam is of utmost importance to facilitate stable plasma-based accelerators. In this contribution, we discuss novel methods for the mitigation of hosing and present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability of drive and witness beam pair in the nonlinear blowout regime. This work enables more precise and comprehensive studies of hosing and hence, for the potential stabilization of future compact plasma-based accelerators.
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TUPML046	Characterization of Self-Modulated Electron Bunches in an Argon Plasma	electron, experiment, solenoid, focusing	1645
	M. Groß, P. Boonpornprasert, Y. Chen, J. Engel, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, R. Niemczyk, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao DESY Zeuthen, Zeuthen, Germany R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff DESY, Hamburg, Germany F.J. Grüner CFEL, Hamburg, Germany F.J. Grüner, A. Martinez de la Ossa University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany T.J. Mehrling, C.B. Schroeder LBNL, Berkeley, USA I. Will MBI, Berlin, Germany
	The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect* the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 10¹³ cm^-3 to 1015 cm^-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing. * M. Gross et al., "Observation of the self-modulation instabil-ity via time-resolved measurements", accepted for publication at Phys. Rev. Lett.
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TUPML047	Optimisation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ	wakefield, acceleration, laser, electron	1648
	G. Loisch, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, M. Krasilnikov, O. Lishilin, A. Oppelt, Y. Renier, F. Stephan DESY Zeuthen, Zeuthen, Germany R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff DESY, Hamburg, Germany F.J. Grüner CFEL, Hamburg, Germany F.J. Grüner, A. Martinez de la Ossa University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	The transformer ratio, the ratio between maximum accelerating field and maximum decelerating field in the driving bunch of a plasma wakefield accelerator (PWFA), is one of the key aspects of this acceleration scheme. It not only defines the maximum possible energy gain of the PWFA but it is also connected to the maximum percentage of energy that can be extracted from the driver, which is a limiting factor for the efficiency of the accelerator. Since in linear wakefield theory a transformer ratio of 2 cannot be exceeded with symmetrical drive bunches, any ratio above 2 is considered high. After the first demonstration of high transformer ratio acceleration in a plasma wakefield at PITZ, the photoinjector test facility at DESY, Zeuthen site, limiting aspects of the transformer ratio are under investigation. This includes e.g. the occurrence of bunch instabilities, like the transverse two stream instability, or deviations of the experimentally achieved bunch shapes from the ideal.
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TUPML049	Comparison of Fourier Signal and Error Analysis Techniques for Identifying the Self-Modulation Frequency of a Proton Bunch	proton, wakefield, electron, experiment	1651
	S.J. Gessner CERN, Geneva, Switzerland
	The AWAKE experiment uses an ultra-high energy proton beam to create large amplitude wakefields for accelerating electrons in plasma. The proton beam is much longer than the plasma wavelength, and must be formed into small, sub- wavelength sized beamlets before it can effectively drive the wake. These beamlets are referred to as micro-bunches and are formed by the plasma self-modulation instability. An im- portant aspect of AWAKE is to measure the depth, frequency, and stability of the modulation, as this provides critical in- formation for establishing the presence of a high-amplitude wakefield driven by a self-modulation proton bunch. This paper discusses Fourier Analysis techniques for measuring the modulation frequency and compares error estimation techniques that work for both small and large datasets. On behalf of the AWAKE Collaboration.
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TUPML051	Studies of Collision and Compression of Pulsed Plasmas Generated by Coaxial Accelerators	electron, experiment, ion-source, simulation	1653
	T. Manegold, C. Benzing, M. Iberler, J. Jacoby, P. Mahmoodi Tavana, A. Müller-Münster, B. Podßus IAP, Frankfurt am Main, Germany
	This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 10¹⁵cm^-3. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 10¹⁸cm^-3.
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TUPML059	Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator	laser, beam-loading, simulation, electron	1670
	X. Li, P.A.P. Nghiem IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France A. Mosnier CEA/IRFU, Gif-sur-Yvette, France
	GeV-scale laser-plasma accelerating modules can be integrated into a multi-staged plasma linac for driving compact X-ray light sources or future colliders. Such a plasma module, operating in the quasi-linear regime, has been designed for the 5 GeV laser plasma acceleration stage (LPAS) of the EuPRAXIA project. Although it can be employed to optimize the total energy spread, the beam loading effect introduces an non-negligible slice energy spread to the beam. In this paper, we study the slice energy spread from linear theory, establishing a relationship between it and the laser-plasma parameters. To reduce the slice energy spread, simulations have been carried out for various plasma densities and laser strengths. The results will be discussed and compared with the theory.
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TUPML066	Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices	simulation, emittance, scattering, cavity	1696
	P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA J.S. Ellison IIT, Chicago, Illinois, USA
	Funding: Work supported by the Department of Energy. New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.
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TUPML070	Laser Ablation Plasma with Solenoid Field Confinement	laser, solenoid, target, ion-source	1706
	G.C. Wang, Q. Jin, L.T. Sun, J. Zhang, X.Z. Zhang, H.W. Zhao, H. Zhao IMP/CAS, Lanzhou, People's Republic of China
	Funding: This work is supported by National Natural Science Foundation of China (Grant Nos. 11722547, 11605263 and 11505257) and West Light Foundation of The Chi-nese Academy of Sciences (Grant Nos. 29Y637020) A Laser Ion Source (LIS) can produce high charge state and high intensity ion beams (~emA), especially refracto-ry metallic ion beams, which makes it a promising candi-date as an ion source for heavy ion cancer therapy facili-ties and future accelerator complexes, where pulsed high intensity and high charged heavy ion beams are required. However, it is difficult for LIS to obtain a long pulse width while ensuring high current intensity, thus limiting the application of LIS. To solve the conflict, magnetic fields are proposed to confine the expansion of the laser produced plasma. With a solenoid along the normal direc-tion to the target surface, the lateral adiabatic expansion of the laser ablation plasma is suppressed which extends the pulse width of the ion beam effectively.
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TUPML079	A Start to End Simulation of the Laser Plasma Wakefield Acceleration Experiment at ESCULAP	electron, laser, acceleration, wakefield	1731
	K. Wang, C. Bruni, K. Cassou, V. Chaumat, N. Delerue, D. Douillet, S. Jenzer, V. Kubytskyi, P. Lepercq, H. Purwar LAL, Orsay, France E. Baynard, M. Pittman CLUPS, Orsay, France J. Demailly, O. Guilbaud, S. Kazamias, B. Lucas, G. Maynard, O. Neveu, D. Ros CNRS LPGP Univ Paris Sud, Orsay, France D. Garzella CEA, Gif-sur-Yvette, France R. Prazeres CLIO/ELISE/LCP, Orsay, France
	We present a start to end (s2e) simulation of the Laserplasma Wake Field Accelerator (LPWA) foreseen as the ESCULAP project. We use a photo injector to produce a 5 MeV 10 pC electron bunch with a duration of 1 ps RMS, it is boosted to 10 MeV by a S-band cavity and then compressed to 74 fs RMS (30 fs FWHM) by a magnetic compression chicane (dogleg). After the dogleg, a quadrupole doublet and a triplet are utilized to match the Twiss parameters before injecting into the subsequent plasma wakefield. A 40 TW laser is used to excite plasma wakefield in the 10 cm plasma cell. An optimized configuration has been determined yielding at the plasma exit an electron beam at 180 MeV with energy spread of 4.2%, an angular divergence of 0.6 mrad and a duration of 4 fs.
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WEPAF026	Beam Induced Fluorescence Measurements of 100 keV Deuterons in LIPAc Accelerator	electron, injection, detector, emittance	1877
	R. Varela, A. Guirao, L.M. Martínez, J. Mollá, I. Podadera CIEMAT, Madrid, Spain T. Akagi, R. Ichimiya, Y. Ikeda, M. Sugimoto QST, Aomori, Japan B. Bolzon, N. Chauvin CEA/IRFU, Gif-sur-Yvette, France P. Cara Fusion for Energy, Garching, Germany H. Dzitko F4E, Germany J. Knaster IFMIF/EVEDA, Rokkasho, Japan
	Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project FIS2013-40860-R The LIPAc accelerator will be a linear CW deuteron accelerator capable of delivering a 9 MeV, 125 mA beam which aims to validate the technology that will be used in the future high power accelerator-driven neutron source, IFMIF. In summer 2017 a campaign of measurements was done during the injector commissioning, in which a Fluorescence Profile Monitor based on an Intensified CID camera (ICID) was used to measure the beam transverse profile at the extraction of the ion source. In this contribution we review the design of the ICID, its performance and discuss the measurements carried out. The performance of ICID monitors for its use in future accelerators will be assessed.
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WEPAF057	Electron Beam Diagnostics Concept for the ELI LUX Project	electron, diagnostics, laser, undulator	1954
	K.O. Kruchinin, D. Kocon, A.Y. Molodozhentsev, L. Pribyl ELI-BEAMS, Prague, Czech Republic A. Lyapin JAI, Egham, Surrey, United Kingdom
	Nowadays the popularity of Laser Wakefield Accelerators (LWFA) is increasingly growing. Although the quality of the beams produced by LWFA is still lower than provided by conventional accelerators, they have great potential to be considered as a new basis for future FELs and even colliders. Laser Undulator X-ray (LUX) source is being commissioned at ELI-beamlines in Czech Republic. The goal of this machine is to provide photon beam in so called "water window" wavelength region for user experiments. Possible upgrade of the facility towards the LWFA based FEL is also considered. The electron beam diagnostics is absolutely crucial for achieving the aim of LUX. Specific properties of the beam produced by current LWFA, such as low charge, poor beam stability, big beam divergence and energy spread, require rethinking and adaptation of the conventional diagnostic tools and, in some cases, development of new ones. Ideally, they have to be compact, stable, non-invasive and allow measurements in single-shot mode. In this report we will present an overview and design considerations for the LUX electron beam main diagnostics. We will also discuss the hardware status and future plans.
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WEPAF070	Commissioning of Beam Instrumentation at the CERN AWAKE Facility After Integration of the Electron Beam Line	electron, proton, laser, experiment	1993
	I. Gorgisyan, C. Bracco, S. Burger, S. Döbert, S.J. Gessner, E. Gschwendtner, L.K. Jensen, S. Jensen, S. Mazzoni, D. Medina, K. Pepitone, L. Søby, F.M. Velotti, M. Wendt CERN, Geneva, Switzerland M. Cascella, S. Jolly, F. Keeble, M. Wing UCL, London, United Kingdom V.A. Verzilov TRIUMF, Vancouver, Canada
	The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a project at CERN aiming to accelerate an electron bunch in a plasma wakefield driven by a proton bunch. The plasma is induced in a 10 m long Rubidium vapour cell using a pulsed Ti:Sapphire laser, with the wakefield formed by a proton bunch from the CERN SPS. A 16 MeV electron bunch is simultaneously injected into the plasma cell to be accelerated by the wakefield to energies in GeV range over this short distance. After successful runs with the proton and laser beams, the electron beam line was installed and commissioned at the end of 2017 to produce and inject a suitable electron bunch into the plasma cell. To achieve the goals of the experiment, it is important to have reliable beam instrumentation measuring the various parameters of the proton, electron and laser beams such as transverse position, transverse profile as well as temporal synchronization. This contribution presents the status of the beam instrumentation in AWAKE, including the new instruments incorporated into the system for measurements with the electron beam line, and reports on the performance achieved during the AWAKE runs in 2017. Gschwendtner E., et al. "AWAKE, the Advanced Proton Driven Plasma Wakefield Experiment at CERN", NIM A 829 (2016)76-82
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WEPAF074	Non-invasive Beam Diagnostics with Cherenkov Diffraction Radiation	photon, radiation, detector, electron	2005
	T. Lefèvre, M. Bergamaschi, O.R. Jones, R. Kieffer, S. Mazzoni CERN, Geneva, Switzerland L.Y. Bartnik, M.G. Billing, Y.B.P. Bordlemay Padilla, J.V. Conway, M.J. Forster, J.P. Shanks, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Bergamaschi, P. Karataev Royal Holloway, University of London, Surrey, United Kingdom V.V. Bleko, A.S. Konkov, J.S. Markova, A. Potylitsyn TPU, Tomsk, Russia L. Bobb DLS, Oxfordshire, United Kingdom K. Lekomtsev JAI, Egham, Surrey, United Kingdom
	Based on recent measurements of incoherent Cherenkov Diffraction Radiation (ChDR) performed on the Cornell Electron Storage Ring, we present here a concept for the centering of charged particle beams when passing close to dielectric material. This would find applications as beam instrumentation in dielectric capillary tubes, typically used in novel accelerating technologies, as well as in collimators using bent crystals for high-energy, high-intensity hadron beams, such as the Large Hadron Collid-er or Future Circular Collider. As a charged particle beam travels at a distance of a few mm or less from the surface of a dielectric material, incoherent ChDR is produced inside the dielectric. The photons are emitted at a large and well-defined angle that allows their detection with a limited contribution of background light. A set of ChDR detectors distributed around a dielectric would enable both the beam position and tilt angle to be measured with a good resolution.
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WEPAG002	Tunable Q-Factor Gas-Filled RF Cavity	cavity, coupling, hadron, simulation	2064
	M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, K. Yonehara, R.M. Zwaska Fermilab, Batavia, Illinois, USA M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer Muons, Inc, Illinois, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795. Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.
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WEPAK001	Intense Neutrino Source Front End Beam Diagnostics System R&D	cavity, detector, target, hadron	2077
	K. Yonehara, M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, R.M. Zwaska Fermilab, Batavia, Illinois, USA M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer Muons, Inc, Illinois, USA
	Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795. We overview the front end beam diagnostic system R&D to prepare operation of a multi-MW proton beam for intensity frontier Neutrino experiments. One of critical issues is shorter life time of a detector with higher beam intensity due to radiation damage. We show a possible improvement of the existing ion chamber based detector, and a study of a conceptually new radiation-robust detector which is based on a gas-filled RF resonator.
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WEPAL065	Development of a Gas Sheet Beam Profile Monitor for IOTA	simulation, detector, space-charge, proton	2326
	S. Szustkowski, B.T. Freemire Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay Northern Illinois Univerity, DeKalb, Illinois, USA D.J. Crawford Fermilab, Batavia, Illinois, USA
	Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program A nitrogen gas sheet will measure the two dimensional transverse profile of the 2.5 MeV proton beam in IOTA. The beam lifetime is limited by the interaction with the gas, thus a minimally invasive instrument is required. To produce a gas sheet with the desired density and thickness, various nozzle types are being investigated, including rectangular capillary tubes for gas injection and skimmers for final shaping of the gas. It is essential to meet vacuum requirements in the interaction chamber while maintaining the precise thickness and density of the gas, without significantly affecting the beam lifetime. The current design of a gas sheet beam profile monitor and present status will be discussed.
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WEPMF061	High Gradient Pulsed Quadrupoles for Novel Accelerators and Space Charge Limited Beam Transport	quadrupole, focusing, electron, wakefield	2505
	C. Tenholt CERN, Geneva, Switzerland G. Loisch, F. Stephan DESY Zeuthen, Zeuthen, Germany B. Marchetti DESY, Hamburg, Germany
	Novel acceleration schemes like plasma wake-field based accelerators demand for high gradient focusing elements to match the Twiss parameters in the plasma to the transport lattice of the conventional accelerator beamlines, with typically much higher beta-functions. There are multiple candidates for achieving high gradient focusing fields, each one having certain drawbacks. Permanent magnets are limited in tunability, plasma lenses might degrade the transverse beam quality significantly and conventional magnets cannot reach very high gradients and often cannot be placed in direct proximity of the plasma accelerator because of their size. In this paper we present design considerations and simulations on compact, high gradient, pulsed quadrupoles, that could be used e.g. for final focusing of space charge dominated bunches into a LWFA (Laser Wake-Field Accelerator) at SINBAD or other facilities with similar demands. The target design gradient is 200 T/m at a physical aperture on the order of 10 mm.
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WEPMK012	Update on Plasma Processing R&D for LCLS-II	cavity, HOM, experiment, SRF	2656
	P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans, S.-H. Kim, K.E. Tippey ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.
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WEPML038	Plasma Window as a Pressure Valve for FAIR	cathode, experiment, electron, vacuum	2776
	B. F. Bohlender, M. Iberler, J. Jacoby IAP, Frankfurt am Main, Germany A. Michel Goethe Universität Frankfurt, Frankfurt am Main, Germany
	Funding: Funded by BMBF, Ref. No: 05P15 RFRBA and HIC for FAIR This contribution shows the progress in the development of a plasma window at the institute for applied physics at Goethe University Frankfurt. A plasma window* is a membrane free transition between two regions of different pressure, enabling beam transmission from a rough vacuum area (~1 mbar) to a higher pressure (up to 1 bar) region on short length scales. In comparison to differential pumping stages a length reduction by a factor of up to 100 is achievable, while the absence of a solid membrane yields prolonged operation time. The sealing effect is based on the high temperature arc discharge sustained in a cooled copper channel between the pressure regimes. Due to a bulk temperature around 10,000K** the viscosity of the gas is dramatically increased, leading to a slower gas flow, enabling a higher pressure gradient. This contribution will present first results regarding the pressure gradient in dependence of the discharge current and the aperture. Until now, a pressure factor around 100 has been established for well over 50 min. This contribution goes along with the one from Mr. A. Michel, he focuses on the spectroscopic analysis of the arc plasma. A. Hershcovitch, J. Appl. Phys., AIP Publishing (1995) 78, 5283 *Y.E. Krasik et al., "Plasma Window Characterization", J. Appl. Phys., AIP Publishing (2007) 101, 053305.
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THPAF005	Simulations of Modulator for Coherent Electron Cooling	electron, simulation, bunching, quadrupole	2953
	J. Ma, V. Litvinenko, G. Wang BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA
	Highly resolved numerical simulations have been performed using the code SPACE for the modulator, the first section of the Coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Simulation results have been benchmarked with analytical solution using uniform electron beam with realistic thermal velocities. Electron bunches with Gaussian distribution and quadrupole field with realistic settings have been applied in the simulations to predict the modulation process and final bunching factors induced by ions with reference and off-reference energies in the CeC experiment at BNL RHIC.
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THPAF032	Simulation Study of an RF Injector for the LWFA Configuration at EuPRAXIA	linac, injection, emittance, simulation	3025
	J. Zhu, R.W. Aßmann, A. Ferran Pousa, B. Marchetti, P.A. Walker DESY, Hamburg, Germany
	The Horizon 2020 Project EuPRAXIA (EuropeanPlasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with multi-GeV electron beams using a plasma accelerator. LWFA with external injection from an RF accelerator is one of the most promising configurations. In order to achieve the goal parameters for the 5 GeV, 30 pC electron beam at the entrance of the undulator, a high-quality electron beam with bunch length of less than 10 fs (FWHM) and matched beta functions (~1 mm) at the plasma entrance is required. In addition, from the compactness point of view, the injection energy is desired to be as low as possible. A hybrid compression scheme is considered in this paper and a detailed start-to-end simulation is presented.
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THPAK043	Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures	GPU, simulation, kicker, HOM	3309
	Zh.C. Liu IHEP, Beijing, People's Republic of China J. Qiang LBNL, Berkeley, California, USA
	The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.
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THPAK083	An s-Based Symplectic Spectral Space Charge Algorithm	space-charge, optics, simulation, proton	3425
	N.M. Cook, D.T. Abell, D.L. Bruhwiler, J.P. Edelen, C.C. Hall, S.D. Webb RadiaSoft LLC, Boulder, Colorado, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340. Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab.
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THPAK094	High Acceptance Beamline for the Capture of a Laser Wakefield Accelerated Beam	quadrupole, focusing, permanent-magnet, laser	3456
	B.D. Muratori, J.K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom K.A. Dewhurst University of Manchester, Manchester, United Kingdom K.A. Dewhurst, J.K. Jones, H.L. Owen Cockcroft Institute, Warrington, Cheshire, United Kingdom H.L. Owen UMAN, Manchester, United Kingdom
	Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK094
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THPAK107	Space-Charge Hamiltonian with a Space Coordinate as Independent Variable	space-charge, TRIUMF, vacuum, synchrotron	3484
	T. Planche, P. M. Jung, S.D. Rädel TRIUMF, Vancouver, Canada
	We present a version of the Low Lagrangian tailored to treat space-charge effects in particle accelerators: the Lagrangian is relativistic and uses a space coordinate as the independent variable. From this Lagrangian we obtain the corresponding Hamiltonian. From the Hamiltonian we obtain equations of motion for the 8 canonical variables, which can be plugged into a symplectic numerical integrator. We will finally discuss the possibility of numerically solving this problem using an explicit symplectic integrator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK107
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THPAK121	Accelerator Optimization through LIV. DAT	proton, radiation, experiment, wakefield	3526
	C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: LIV. DAT is supported by the STFC under contract ST/P006752/1. The Liverpool Big Data Science (LIV. DAT) Center for Doctoral Training (CDT) is a hub for training students in managing, analysing and interpreting large, complex datasets and high rates of data flow. LIV. DAT offers a unique training approach addressing some of the biggest challenges in data intensive science to tackle a growing skills gap. It currently provides training to a cohort of almost 20 PhD students. Their research projects address R&D challenges in astronomy, nuclear, particle and accelerator physics. This contributions presents initial research results from modeling studies of the physics and biology of proton beam therapy using a Monte Carlo approach, as well as plasma-beam interaction in the cases of AWAKE and EuPRAXIA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK121
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THPAK136	Wide-Ranging Genetic Research of Matching Line Design for Plasma Accelerated Beams with GIOTTO	emittance, electron, target, FEL	3561
	M. Rossetti Conti Universita' degli Studi di Milano & INFN, Milano, Italy A. Bacci, A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy A. Giribono, C. Vaccarezza INFN/LNF, Frascati (Roma), Italy
	GIOTTO is a code based on a Genetic Algorithm, being used in the field of particles accelerators for some years-. Its main use concerns beam-dynamics optimizations for low energy linacs, or injectors, where the beam space-charge plays an important role on its dynamics. Typical optimizations regard the Velocity Bunching technique or, more generally, the emittance and energy spread minimization. Recent improvements in GIOTTO, here discussed, have added the important capability to solve problems with a wide research domain, making GIOTTO able to design a beam Transfer Line (TL) from scratch*. The code, taking as input the TL length and the optics elements, can define the correct lattice of the line that transports and matches the beam from the linac to the undulators of an FEL, finding the right gradients, positions and dimensions for the optics elements by exploring the parameters values in selected ranges. Further, the introduction of Twiss parameters into the fitness function makes GIOTTO a powerful tool in the design of highly different beam lines. Lastly, a new routine for the statistical analysis of parameters jitters effects on the beam is under development. Bacci et al, NIM-B, 263, 488 (2007) Bacci et al, presented at PAC'07, THPAN031 Bacci et al, presented at IPAC'16, WEPOY039 ***Rossetti Conti et al, NIM-A (2018, in press)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK136
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THPAL065	Improving the Work Function of Nitrogen-Doped Niobium Surfaces for SRF Cavities by Plasma Processing	cavity, niobium, SRF, accelerating-gradient	3802
	K.E. Tippey, R. Afanador, M. Doleans, S.-H. Kim, J.D. Mammosser, C.J. McMahan ORNL, Oak Ridge, Tennessee, USA M. Martinello Fermilab, Batavia, Illinois, USA
	Funding: DOE research grant FWP-ERKCSA2; DOE contract DE-AC05-00OR22725 Work function and surface chemistries of SiC-polished, electropolished, and nitrogen-doped niobium coupons were analyzed before and after plasma processing using a neon-oxygen gas mixture. These studies represent an initial enquiry into the feasibility of applying the plasma processing technique designed at ORNL for the Spallation Neutron Source (SNS) to the nitrogen-doped Nb cavities for the Coherent Light Source II (LCLS-II). Work function of all measured samples was increased after plasma processing, which indicates the strong potential of the plasma processing technique as a tool for increasing the accelerating gradient of nitrogen-doped cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL065
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THPAL069	Simulation of a 10 mm Diameter Cascaded Plasma Window	cathode, simulation, vacuum, experiment	3812
	P.P. Gan, S. Huang, Y.R. Lu, S.Z. Wang, K. Zhu PKU, Beijing, People's Republic of China
	As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL069
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THPAL083	A Test Facility for Developments in Ion Source Plasma Power Supplies	power-supply, controls, ion-source, electronics	3845
	R.E. Abel, D.C. Faircloth, S.R. Lawrie, J.H. Macgregor, M. Perkins STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	A new test facility is being designed and constructed at the ISIS spallation neutron source, Rutherford Appleton Laboratory, for the purpose of developing and experimenting with new plasma power supply topologies and modes of operation. The test facility will allow better control of power supply parameters such as discharge pulse current and plasma ignition voltage along with the possibility for closed loop feedback control. The design and technical construction details are presented with an overview of the plasma power supply developments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL083
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THPAL095	Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory	cathode, electron, gun, laser	3865
	A.N. Hannah, J.A. Conlon, L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom V. R. Dhanak The University of Liverpool, Liverpool, United Kingdom L.B. Jones, B.L. Militsyn Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Lederer DESY Zeuthen, Zeuthen, Germany S. Lederer DESY, Hamburg, Germany
	The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10^-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL095
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THPAL102	Design a High Power Pulse Transformer for C-band Klystron Modulator	flattop, klystron, high-voltage, FEL	3875
	Y.F. Liu, Z.H. Chen, M. Gu, Y. Wu, Q. Yuan, X.X. Zhou SINAP, Shanghai, People's Republic of China
	Shanghai soft X-ray Free Electron Lasers (SXFEL) first uses C band accelerator structure to accelerate electrons at SINAP. SXFEL is an X-ray free electron laser facility, which requests very stable amplitude stability and very tight tolerances of phase jitter. 50MW C-band klystron and 110MW modulator is used to provide power supply for accelerator structure. Typical specifications of the modulator are peak beam voltage 350KV, peak beam current 320A, 10Hz repetition rate, 3us flat-top pulse width. In order to meet these demands, we developed a reliable and stable high power pulse transformer. In this paper, the analysis and design of high power pulse transformer for C band klystron modulator are presented. The methods of shortening rise time, diminishing droop and diminishing flat top oscillation are highlighted. Detailed design, simulation and relevant experimental results are given. The relevant experiments show that this pulse transformer can meet the requirement of 50MW C band klystron.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL102
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THPMF014	First Experiments at the CLEAR User Facility	electron, experiment, radiation, operation	4066
	R. Corsini, A. Curcio, S. Curt, S. Döbert, W. Farabolini, D. Gamba, R. Garcia Alia, T. Lefèvre, G. McMonagle, P.K. Skowroński, M. Tali, F. Tecker CERN, Geneva, Switzerland E. Adli, C.A. Lindstrøm, K.N. Sjobak University of Oslo, Oslo, Norway R.M. Jones, A. Lagzda UMAN, Manchester, United Kingdom
	The new "CERN Linear Electron Accelerator for Research" (CLEAR) facility at CERN started its operation in fall 2017. CLEAR results from the conversion of the CALIFES beam line of the former CLIC Test Facility (CTF3) into a new testbed for general accelerator R&D and component studies for existing and possible future accelerator applications. CLEAR can provide a stable and reliable electron beam from 60 to 220 MeV in single or multi bunch configuration at 1.5 GHz. The experimental program includes studies for high gradient acceleration methods, e.g. for CLIC X-band and plasma technology, prototyping and validation of accelerator components, e.g. for the HL-LHC upgrade, and irradiation test capabilities for characterization of electronic components and for medical applications. An overview of the facility capabilities and a summary of the latest results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF014
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THPMF086	Reliability Improvement on Wiggler Period Averaging Approximation	wiggler, FEL, simulation, laser	4281
	K. Hwang, J. Qiang LBNL, Berkeley, California, USA
	Funding: US Department of Energy under Contract no. DEAC02-05CH11231 As the wiggler period averaging is subject to reliability issue, many efforts on FEL codes without such approximations are made at the cost of heavier computation loads. However, efforts toward increasing the reliability of such approximation are few. In this report, we present a new capability of IMPACT code suite based on such approximation with the addition of perturbative corrections to wiggler period averaging error.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF086
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THPMK063	Photocathode Preparation and Characteristics of the Electron Source for the VELA/CLARA Facility	cathode, laser, electron, operation	4442
	T.C.Q. Noakes, D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, M.D. Roper, E.W. Snedden, R. Valizadeh, D.A. Walsh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The VELA and CLARA front end accelerators at Daresbury are test facilities with a focus on FEL research and industrial applications of electron beams. Recently the CLARA injector has been commissioned with acceleration of beam to 50 MeV. For several years a normal conducting 2.5 cell S-band cavity RF gun operated at up to 80 MV/m has been used as the electron source for both VELA and CLARA. For further beam acceleration an S-band travelling wave 2m long cavity has been used. The gun has used several different copper cathodes throughout its operational life, employing different preparation techniques. Oxygen plasma treatment is a well-known procedure for removing hydrocarbon contamination from surfaces whereas Argon plasma treatment also removes contaminants and typically leaves a thinner oxide at the surface. In this study we compare dark current (from field emission), as measured directly after the gun, for these alternate surface preparations and also present results from post-use electron microscopy analysis of the photocathodes. Electromagnetic simulations are used to help explain the results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK063
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THPMK076	Longitudinal Shaping for Beam-Driven Plasma Wakefield Accelerators	electron, linac, FEL, simulation	4477
	Z. Wang, K.Q. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China S. Huang, W. Lu TUB, Beijing, People's Republic of China
	The generation of high quality driven electron beam (high peak current and small beam size) is quite important for the beam-driven plasma accelerator. Besides, a linearly ramped, more exactly, the triangular current distribution is more suitable. In this paper, by adjusting the phase and the amplitude of the harmonic linearizer, the linear ramped current distribution electron beam is generated by the FEL linac. The CSR introduced emittance growth and the jitters of the electron are researched. The electron beam generated by the ramped driven beam in the plasma is researched as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK076
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THPML002	Emittance Preservation in Plasma-Based Accelerators with Ion Motion	emittance, wakefield, background, ECR	4654
	C. Benedetti, E. Esarey, W. Leemans, T.J. Mehrling, C.B. Schroeder LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. DOE under Contract No. DE-AC02-05CH11231. In a plasma-accelerator-based linear collider, the density of matched, low-emittance, high-energy particle bunches required for collider applications can be orders of magnitude above the background ion density, leading to ion motion, perturbation of the focusing fields, and, hence, to beam emittance growth. By analyzing the response of the background ions to an ultrahigh density beam, analytical expressions, valid for non-relativistic ion motion, are obtained for the perturbed focusing wakefield. Initial beam distributions are derived that are equilibrium solutions, which require head-to-tail bunch shaping, enabling emittance preservation with ion motion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML002
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THPML009	Polarized Deuteron Negative Ion Source for Nuclear Physics Applications	polarization, laser, ion-source, electron	4665
	V.G. Dudnikov, M.A. Cummings, R.P. Johnson Muons, Inc, Illinois, USA A.V. Sy JLab, Newport News, Virginia, USA
	The proposed U.S. Electron-Ion Collider (EIC) provides a unique tool to explore the next frontier in Quantum Chromodynamics, the dependence of hadron structure on the dynamics of gluons and sea quarks. Polarized beams are essential to these studies; understanding of the hadron structure cannot be achieved without knowledge of the spin. The existing EIC concepts utilize both polarized electrons and polarized protons/light ion species to probe the sea quark and gluon distributions. Polarized deuterons provide an especially unique system for study by essentially providing a combination of quark and nuclear physics. We note that there are currently no operational polarized deuteron beam sources in the United States. This polarized deuteron source can serve as a polarized deuteron injector for a future EIC, with additional applications in polarimetry and polarized gas targets for experiments at CEBAF or RHIC and would be very useful for our future facilities.
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THPML018	Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses	laser, electron, focusing, target	4690
	C.-Y. Hsieh, S.-H. Chen NCU, Chung Li, Taiwan M.W. Lin National Tsing-Hua University (NTHU), Hsinchu, Taiwan
	Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3. Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly. A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015). ** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML018
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THPML031	Collective Acceleration of Laser Plasma in Non-stationary and Non-uniform Magnetic Field	laser, acceleration, target, experiment	4716
	A.A. Isaev, C.I. Kozlovskij, E.D. Vovchenko MEPhI, Moscow, Russia
	This paper presents the new experimental results concerning acceleration of deuterium ions extracted from laser plasma in the rapid-growing nonuniform magnetic field in order to initiate the nuclear reactions D(d, n)3He and Т (d,n)4He. In order to obtain plasma a laser that generates in Q-switched mode the pulses of infrared radiation (λ = 1.06 μm) with the energy W ≤ 0.85 J and duration of ≈10 ns. In the present study, the velocity of a bunch of a laser plasma at a magnetic field induction rate of 3-10⁸ T/s was experimentally measured, and angular distributions of accelerated particle fluxes were measured in the range from 0 to 30 degrees. The maximum and mean ion velocities were determined by the time-of-flight technique. The proposed system allows the generation of neutrons, including possibly thermonuclear ones, on counterflows using two similar magnetic accelerators located coaxially, facing each other. In this case the problem related to degradation of solid neutron-generating targets is resolved. There also occurs a possibility of fast accumulated running time of packed solid targets at using of deuteron-tritium laser targets.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML031
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THPML033	Towards a Free Electron Laser Using Laser Plasma Acceleration	electron, laser, free-electron-laser, FEL	4723
	A. Loulergue, T. André, I.A. Andriyash, C. Benabderrahmane, P. Berteaud, F. Blache, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Chapuis, M.-E. Couprie, D. Dennetière, Y. Dietrich, J.P. Duval, M. El Ajjouri, T.K. El Ajjouri, A. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitegi, M. Labat, N. Leclercq, A. Lestrade, O. Marcouillé, F. Marteau, P. N'gotta, D. Oumbarek, F. Polack, P. Rommeluère, M. Sebdaoui, K.T. Tavakoli, M. Valléau, J. Vétéran, C. de Oliveira SOLEIL, Gif-sur-Yvette, France S. Bielawski, C. Evain, E. Roussel, C. Szwaj PhLAM/CERLA, Villeneuve d'Ascq, France S. Corde, J. Gautier, J.-P. Goddet, G. Lambert, B. Mahieu, V. Malka, J.P. Rousseau, S. Sebban, K. Ta Phuoc, A. Tafzi, C. Thaury LOA, Palaiseau, France O. S. Kononenko DESY, Hamburg, Germany S. Smartzev Weizmann Institute of Science, Physics, Rehovot, Israel
	Since the laser invention, the advent of X-ray Free Electron Lasers (FEL) half a century later, opens new areas for matter investigation. In parallel, the spectacular development of laser plasma acceleration (LPA) with several GeV beam acceleration in an extremely short distance appears very promising. As a first step, the qualification of the LPA with a FEL application sets a first challenge. Still, energy spread and beam divergence do not meet the state-of-the-art performance of the conventional accelerators and have to be manipulated to fulfill the FEL requirement. We report here on the undulator spontaneous emission measured after a transport manipulation electron beam line, using variable permanent magnet quadrupoles of variable strength for emittance handing and a demixing chicane equipped with a slit for the energy spread. Strategies of control electron beam position and dispersion have been elaborated. The measured undulator radiation provides an insight on the electron beam properties.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML033
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THPML042	Integrating the Lorentz Force Law for Highly-Relativistic Particle-in-Cell Simulations	laser, simulation, acceleration, radiation	4734
	A.V. Higuera, J.R. Cary Tech-X, Boulder, Colorado, USA J.R. Cary CIPS, Boulder, Colorado, USA
	Funding: This work is supported by the DOE under Grants No. DE-SC0011617 and DE-SC0012444, and by DOE/NSF Grant No. DE-SC0012584 Integrating the Relativistic Lorentz Force Law for plasma simulations is an area of current research (, , ). In particular, recent research indicates that interaction with highly-relativistic laser fields is particularly problematic for current integration techniques (*). Here is presented a special-purpose integrator yielding improved accuracy for highly-relativistic laser-particle interactions. This integrator has been implemented in the particle-in-cell code VSim, and the authors present an accuracy and performance comparison with several particle push methods. http://aip.scitation.org/doi/abs/10.1063/1.4979989 https://arxiv.org/abs/1702.04486 * https://arxiv.org/abs/1710.09164 **** http://aip.scitation.org/doi/abs/10.1063/1.4905523
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML042
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THPML043	Optimization of Dielectric Laser-Driven Accelerators	laser, electron, simulation, acceleration	4737
	C.P. Welsch, M.G. Ibison, Y. Wei The University of Liverpool, Liverpool, United Kingdom M.G. Ibison, Y. Wei, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom J.D.A. Smith TXUK, Warrington, United Kingdom G.X. Xia UMAN, Manchester, United Kingdom
	Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191. Dielectric laser-driven accelerators (DLAs) utilizing large electric field from commercial laser system to accelerate particles with high gradients in the range of GV/m have the potential to realize a first particle accelerator ‘on a chip'. Dual-grating structures are one of the candidates for DLAs. They can be mass-produced using available nanofabrication techniques due to their simpler structural geometry compared to other types of DLAs. Apart from the results from optimization studies that indicate the best structures, this contribution also introduces two new schemes that can help further improve the accelerating efficiency in dual-grating structures. One is to introduce a Bragg reflector that can boost the accelerating field in the channel, the other applies pulse-front-tilt operation for a laser beam to help extend the interaction length.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML043
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THPML051	Electron Acceleration by Plasma Wave in the Presence of a Transversely Propagated Laser with Magnetic Field	electron, laser, acceleration, wakefield	4749
	M. Yadav, S. C. Sharma DELTECH, New Delhi, India D.N. Gupta, M. Kaur University of Delhi, Delhi, India
	It has been revealed that a relativistic plasma wave, having an extremely large electric field, may be utilized for the acceleration of plasma particles. The large accelerating field gradient driven by a plasma wave is the basic motivation behind the acceleration mechanism. Such a plasma wave can be excited by a single laser in the form wakefield in laser-plasma interactions. In this paper, we study the enhancement of electron acceleration by plasma wave in presence of a laser* propagated perpendicular to the propagation of the wake wave. Electrons trapped in the plasma wave are effectively accelerated by the additional field of the laser combined with wakefield. The additional resonance provided by the laser field contributes to the large energy gain of electrons during acceleration. The resonant enhancement of electron acceleration has been validated by single particle simulations*. The dependence of energy gain on laser intensity, laser spot size, initial electron energy, and electron trajectories have been investigated. G. D. Tsakiris, C. Gahn, and V. K. Tripathi, Phys. Plasmas 7, 3017 (2000) ** Maninder Kaur, and D. N. Gupta, IEEE, 45, p 2841 - 2847, (2017)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML051
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THPML052	Excitation of Plasma Wave by Lasers Beating in a Collisional and Mild-Relativistic Plasma	laser, electron, damping, ECR	4752
	M. Kaur, D.N. Gupta University of Delhi, Delhi, India
	Funding: Work supported by Department of Science and Technology (DST), Government of India. Excitation of plasma wave by two lasers beating in a collisional dominated relativistic plasma is investigated. We study the energy exchange between a plasma wave and two co-propagating lasers in plasma including the effect of relativistic mass change and electron-ion collisions. Two lasers, having frequency difference equal to the plasma frequency, excite a plasma beat wave resonantly by the ponderomotive force, which obeys the energy and momentum conservation. The relativistic effect and the electron-ion collision both contribute in energy exchange between the interacting waves in the beat-wave acceleration mechanism. Our study shows that the initial phase difference between interacting waves generates a phase mismatch between lasers and plasma wave, which alters the rate of amplitude variations of the interacting waves and, hence, affects the energy exchange between the interacting waves. This study may be crucial to design a compact plasma accelerator in low-intensity regime*. T. Tajima, and J. Dawson, Phys. Rev.Lett. 43, 267(1979) D. N. Gupta, M. S. Hur, and H. Suk, J.Appl. Phys. 100, 103101 (2006) *M. Kaur and D. N. Gupta, EuroPhysics letter 116, 35001 (2016).
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THPML118	The AWAKE Electron Spectrometer	proton, electron, background, radiation	4947
	F. Keeble, M. Cascella, J. A. Chappell, L.C. Deacon, S. Jolly, M. Wing UCL, London, United Kingdom I. Gorgisyan, S. Mazzoni CERN, Geneva, Switzerland P.L. Penna, M. Quattri ESO, Garching bei Muenchen, Germany
	The AWAKE experiment at CERN aims to use a proton driven plasma wakefield to accelerate electrons from 10–20 MeV up to GeV energies in a 10 m plasma cell. We present the design of the magnetic spectrometer which will measure the electron energy distribution. Results from the calibration of the spectrometer's scintillator and optical system are presented, along with a study of the backgrounds generated by the 400 GeV SPS proton beam.
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MOZGBE1

Development of Gas Stripper at RIBF

acceleration, target, electron, heavy-ion

41

H. Imao
RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan

Charge strippers are almost inevitable for accelerations in heavy-ion accelerator complex. The fixed solid strip-pers including carbon-foil strippers are difficult to be used in on-going or upcoming new-generation in-flight RI beam facilities, e.g., RIBF (RIKEN, Japan), FAIR (GSI, Germany), FRIB (NSCL/MSU, US), HIAF (IMP, China) and RAON (RISP, Korea). The He gas stripper developed at RIBF is the first successful stripper significantly be-yond the applicable limit of the fixed carbon-foil strip-pers. We discuss the development of the gas strippers at RIBF and overview the related new-generation strippers being developed in the world.

Slides MOZGBE1 [11.797 MB]

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TUXGBE1

Status and Prospects for the AWAKE Experiment

electron, proton, wakefield, experiment

595

M. Turner
CERN, Geneva, Switzerland

The AWAKE Collaboration is pursuing a demonstration of proton-driven plasma wakefield acceleration of electrons. The AWAKE experiment uses a §I{400}{GeV/c} proton bunch from the CERN SPS, with a rms bunch length of 6-§I{15}{cm}, to drive wakefields in a §I10{m} long rubidium plasma with an electron density of 10¹⁴-10¹⁵cm^-3. Since the drive bunch length is much longer than the plasma wavelength (λ_pe<§I{3}{mm}) for these plasma densities, AWAKE performed experiments to prove that the long proton bunch self-modulates in the plasma (2017). The next step is to demonstrate acceleration of electrons in the wakefields driven by the self-modulated bunch (2018). We summarize the concept of the self-modulation measurements and describe the plans and challenges for the electron acceleration experiments.

Slides TUXGBE1 [8.878 MB]

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TUXGBE2

Study of Ultra-High Gradient Acceleration in Carbon Nanotube Arrays

electron, acceleration, wakefield, experiment

599

J. Resta-López, A.S. Alexandrova, V. Rodin, Y. Wei, C.P. Welsch, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom
Y. M. Li, Y. Zhao
UMAN, Manchester, United Kingdom

Solid-state based wakefield acceleration of charged particles was previously proposed to obtain extremely high gradients on the order of 1 − 10 TeV/m. In recent years the possibility of using either metallic or carbon nanotube structures is attracting new attention. The use of carbon nanotubes would allow us to accelerate and channel particles overcoming many of the limitations of using natural crystals, e.g. channeling aperture restrictions and thermal-mechanical robustness issues. In this paper, we propose a potential proof of concept experiment using carbon nanotube arrays, assuming the beam parameters and conditions of accelerator facilities already available, such as CLEAR at CERN and CLARA at Daresbury. The acceleration performance of carbon nanotube arrays is investigated by using a 2D Particle-In-Cell (PIC) model based on a multi-hollow plasma. Optimum experimental beam parameters and system layout are discussed.

Slides TUXGBE2 [27.290 MB]

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TUXGBE3

Status of Plasma-Based Experiments at the SPARC_LAB Test Facility

electron, experiment, focusing, emittance

603

E. Chiadroni, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F.G. Bisesto, E. Brentegani, F. Cardelli, G. Costa, M. Croia, D. Di Giovenale, G. Di Pirro, M. Ferrario, F. Filippi, A. Gallo, A. Giribono, A. Marocchino, L. Piersanti, R. Pompili, S. Romeo, J. Scifo, V. Shpakov, A. Stella, C. Vaccarezza, F. Villa
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
INFN-Roma II, Roma, Italy
M. Marongiu, A. Mostacci
Sapienza University of Rome, Rome, Italy
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
A. Zigler
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

The current activity of the SPARC LAB test-facility is focused on the realization of plasma-based acceleration experiments with the aim to provide accelerating field of the order of several GV/m while maintaining the overall quality (in terms of energy spread and emittance) of the accelerated electron bunch. The current status of such an activity is presented, together with results related to the applicability of plasmas as focusing lenses in view of a complete plasma-based focusing, accelerating and extraction system.

Slides TUXGBE3 [10.258 MB]

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TUXGBE4

Beam Quality Limitations of Plasma-Based Accelerators

electron, laser, injection, acceleration

607

A. Ferran Pousa, R.W. Aßmann
DESY, Hamburg, Germany
A. Martinez de la Ossa
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Plasma-based accelerators are a promising novel technology that could significantly reduce the size and cost of future accelerator facilities. However, the typical quality and stability of the produced beams is still inferior to the requirements of Free Electron Lasers (FELs) and other applications. We present here our recent work in understanding the limitations of this type of accelerators, particularly on the energy spread and bunch length, and possible mitigating measures for future applications, like the plasma-based FEL in the EuPRAXIA design study.

Slides TUXGBE4 [4.905 MB]

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TUPAF039

Electron Cooling Simulation and Experimental Benchmarks at LEIR

electron, experiment, simulation, solenoid

776

A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer
CERN, Geneva, Switzerland

A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.

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TUPAL041

Vacuum Accelerating Tube with Two Symmetrically Located Targets for Neutron Generation

electron, cathode, neutron, target

1097

V.I. Rashchikov, A.A. Isaev, A.E. Shikanov
MEPhI, Moscow, Russia

Original neutron generator* on the base of pulse accelerating vacuum tube with two targets, symmetrically located on the both sides of deuteron source is discussed. Two immersion lenses in front of each other uses as accelerating and focusing systems. Lenses cathodes are Faraday cups with targets for neutron production on the bottom. Symmetric ring magnetic elements cover immersion lenses for correcting focusing conditions. Computer simulation allows us to choose electrodes geometry and accelerating pulse value for electron flow from ion-electron emission oscillate between the targets and provide device operate as reflective triode. Estimations of neutron flow and spatio-temporal neutron field structure are done.
* Patent RF N2467526, 14.06.2011

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TUPAL042

On Possibility of Reflective Triode Uses for Thermonuclear Neutron Generation in Budker-Post Trap with Pulsed Magnetic Field

neutron, proton, electron, focusing

1100

V.I. Rashchikov, A.N. Didenko, A.A. Isaev, K.I. Kozlovskiy, V.L. Shatokhin, A.E. Shikanov, E.D. Vovchenko
MEPhI, Moscow, Russia

Scheme for thermonuclear neutron generation in compact Budker-Post trap with barrel-shaped pulsed magnetic field produced by two symmetrically located thin coils with diameter not exceed 0.05 m is proposed. During neutron generation in the trap simultaneously forms plasma which include hydrogen nuclides with density up to 10¹³ m-3 and two pulsed counter hydrogen nuclides flows accelerated in the diodes. Diodes consist of transparent anode with the form of sphere sector symmetrically covered by the same form grounded cathode. Diodes located symmetrically in front of each other, coaxially to magnetic trap. Computer simulation shows possibility to generate up to 1010 neutrons per pulse for deuterium-tritium compound in the diode system with transverse dimension ~0.1 m, amplitude and accelerating pulse duration 5.105 V and 100 nsec. The value of magnetic induction in the center of the trap should be approximately equal to 20 T.

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TUPAL043

Simulations of the Electron Column in IOTA

electron, proton, space-charge, simulation

1103

B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
C.S. Park
Korea University Sejong Campus, Sejong, Republic of Korea
G. Penn
LBNL, Berkeley, California, USA
V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program
Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied.

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TUPAL057

Preliminary Experiments in Caesium Delivery and Gettering on the ISIS Vespa Source

experiment, ion-source, operation, site

1144

T. M. Sarmento, R.E. Abel, D.C. Faircloth, S.R. Lawrie, J.H. Macgregor, M. Whitehead, T. Wood
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Caesium capture by graphite at various temperatures 20- 300°C in the VESPA ion source test stand was explored in a preliminary experiment. An accompanying experiment was set up to evaluate the control of caesium boiler delivery in the various ISIS penning sources. Results indicate Cs flux fluctuates at constant settings, which must be accounted for to interpret graphite gettering results. Future studies to identify the cause of fluctuations are considered, and a more rigorous experiment to study the use of graphite is introduced.

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TUPML014

CO2 CPA Laser Development for User Experiments in Advanced Accelerators and Radiation Sources

laser, experiment, optics, operation

1556

M.N. Polyanskiy, M. Babzien, M.A. Palmer, I. Pogorelsky
BNL, Upton, Long Island, New York, USA

The ATF* is a National User Facility for advanced research in accelerator physics and technology. The ATF's terawatt CO2 laser is a unique scientific instrument allowing researchers to explorer new particle acceleration mechanisms and to study light/matter interaction at an order-of-magnitude longer photon wavelengths compared to the majority of other laser research facilities (λ≈10μm). Continuous development over more than two decades brought the ATF's CO2 laser to the limit of peak power achievable in a conventional gas laser MOPA configuration (in ATF's amplifier geometry this is ~0.5 TW in routine operation, and up to 2 TW in some experiments). To overcome this limit, we employ, for the first time in a gas laser, a chirped-pulse amplification (CPA) scheme. The goal of our current research and development effort is to demonstrate 3-5 TW peak power at the system output and to reliably deliver a large fraction of this power as a high-quality beam to a range of user experiments. Achieving this goal will lay the ground work for implementation of a >10 TW mid-IR laser system "BESTIA" that is currently being constructed as a part of the ATF-II project.
*Accelerator Test Facility at Brookhaven National Laboratory

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TUPML015

Influence of Ionization and Beam Quality on Interaction of Tw-Peak Co2 Laser With Hydrogen Plasma

laser, simulation, electron, experiment

1560

P. Kumar, V. Samulyak
SBU, Stony Brook, USA
V. Samulyak, K. Yu
BNL, Upton, Long Island, New York, USA

3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombination rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.

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TUPML017

Longitudinal Phase Space Reconstruction at FLASHForward Using a Novel Transverse Deflection Cavity, PolariX-TDS

experiment, dipole, simulation, lattice

1567

R.T.P. D'Arcy, A. Aschikhin, P. González Caminal, V. Libov, J. Osterhoff
DESY, Hamburg, Germany

The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration (PWFA) experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams are assessed for their capability to drive a free-electron laser. The ultra short, low emittance, and low energy spread properties of bunches produced from certain PWFA injection schemes naturally lend themselves to this task. However, these bunch lengths, typically in the few femtosecond range, are difficult to temporally resolve with traditional diagnostic methods. In order to longitudinally diagnose these bunches it is necessary to utilise the properties of a transverse RF deflecting cavity operating in a high-frequency regime. It is proposed that this type of X-band transverse deflection system, styled the PolariX-TDS due to its novel variable polarisation feature, will be introduced to the FLASHForward beam line in order to perform these single-shot longitudinal phase space measurements. This paper will concern itself with the efficacy of longitudinally reconstructing PWFA-bunches expected at FLASHForward with this TDS, with a focus on the variable bunch properties expected from early commissioning of the experiment.

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TUPML021

A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator

laser, electron, undulator, quadrupole

1577

K.A. Dewhurst, H.L. Owen
UMAN, Manchester, United Kingdom
E. Brunetti, D.A. Jaroszynski, S.M. Wiggins
USTRAT/SUPA, Glasgow, United Kingdom
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.D. Muratori
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by the UK Science and Technology Facilities Council, Grant No. ST/G008248/1.
The Cockcroft Beamline is to be installed at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). The beamline is designed to transport 1 GeV electrons from a laser wakefield acceleration (LWFA) source to a pair of transverse gradient undulators. The project aims to produce X-ray undulator radiation in the first phase and free-electron laser (FEL) radiation in the second phase. The total beamline will be less than 23 m long, thus the Cockcroft Beamline has the potential to be the UK's first compact X-ray FEL. Here we present the main features of the beamline design.

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TUPML022

Assessment of Transverse Instabilities in Proton Driven Hollow Plasma Wakefield Acceleration

proton, electron, wakefield, focusing

1581

Y. M. Li, G.X. Xia, Y. Zhao
UMAN, Manchester, United Kingdom
S.J. Gessner
CERN, Geneva, Switzerland

Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the witness beam quality. In this paper, by means of the 2D cartesian particle-in-cell simulations, we examine the potentially detrimental effects induced by the driving beam-channel offset and initial driver tilt, and then propose and assess the solutions to these driver inaccuracy issues.

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TUPML023

Amplitude Enhancement of the Self-Modulated Plasma Wakefields

proton, wakefield, focusing, ECR

1585

Y. M. Li, G.X. Xia, Y. Zhao
UMAN, Manchester, United Kingdom
K.V. Lotov, A. Sosedkin
Budker INP & NSU, Novosibirsk, Russia

Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.

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TUPML030

Optimisation of D- Ion Production in a Multicusp Ion Source

ion-source, electron, extraction, dipole

1609

A.M. George, M.P. Dehnel, S.V. Melanson, D.E. Potkins
D-Pace, Nelson, British Columbia, Canada
N. Broderick
University of Auckland, Auckland, New Zealand
H.C. McDonald, C. Philpott
BSL, Auckland, New Zealand

D-Pace's multicusp ion source achieves high beam cur-rents for negative hydrogen ions in both the TRIUMF-licensed filament-powered ion source (~18 mA) and the University of Jyväskylä-licensed RF-powered ion source (~8 mA) [1]. It is well known that ion sources producing negative deuterium ions achieve lower beam currents compared to similar negative hydrogen ion sources and indeed we have found that negative deuterium ion beam currents in our sources are typically 1/3 that of negative hydrogen beam currents. The reasons behind this are not completely understood, but factors such as the magnetic field strength and the electron temperature are believed to play a major role and offer the potential for significant optimisation. In this paper, we look into the issues surrounding swapping of deuterium for hydrogen in our ion source by studying the properties of plasmas and extracted currents with different magnetic field strengths and gas flows.

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TUPML036

ALEGRO, the Advanced LinEar collider study GROup

collider, laser, linear-collider, acceleration

1619

P. Muggli
MPI, Muenchen, Germany
B. Cros
CNRS LPGP Univ Paris Sud, Orsay, France

We briefly describe activities of ALEGRO, the Advanced LinEar collider study GROup.

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TUPML040

Status of the Transverse Diagnostics at FLASHForward

electron, laser, wakefield, diagnostics

1630

P. Niknejadi, R.T.P. D'Arcy, A. Knetsch, V. Libov, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper
DESY, Hamburg, Germany
M. Kaluza, M.B. Schwab, A. Sävert, C. Wirth
IOQ, Jena, Germany
M. Kaluza
HIJ, Jena, Germany
T.J. Mehrling
LBNL, Berkeley, USA
C.A.J. Palmer
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

Funding: Helmholtz Institute, Bundesministerium für Bildung und Forschung, and European Union‘s Horizon 2020 research and innovation program.
Density modulations in plasma caused by a high-intensity laser or a high charge density electron pulse can generate extreme acceleration fields. Acceleration of electrons in such fields may produce ultra-relativistic, quasi-monoenergetic, ultra-short electron bunches over distances orders of magnitudes shorter than in state-of-the-art radio-frequency accelerators. FLASHForward is such a beam-driven plasma wakefield accelerator (PWFA) project at DESY with the goal of producing, characterizing, and utilizing such beams. Temporal characterization of the acceleration process is of crucial importance for improving the stability and control in PWFA beams. While measurement of the transient field of the femtosecond bunch in a single shot is challenging, in recent years novel techniques with great promise have been developed** ***. This work discusses the plans and status of the transverse diagnostics at FLASHForward.
*A. Aschikhin et. al., NIMA , Volume 806 (11 January 2016) pp. 175-183.
**A. Buck et al., Nature Physics 7, (2011) 543.
***C. J. Zhang et al., Phys. Rev. Lett. 119 (2017) 064801.

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TUPML041

Two-Stage Laser-Driven Plasma Acceleration With External Injection for EuPRAXIA

electron, laser, acceleration, wakefield

1634

E.N. Svystun, R.W. Aßmann, U. Dorda, A. Ferran Pousa, T. Heinemann, B. Marchetti, P.A. Walker, M.K. Weikum, J. Zhu
DESY, Hamburg, Germany
A. Ferran Pousa, T. Heinemann, A. Martinez de la Ossa
University of Hamburg, Hamburg, Germany
T. Heinemann
USTRAT/SUPA, Glasgow, United Kingdom

The EuPRAXIA (European Particle Research Accelerator with eXcellence In Applications) project aims at producing a conceptual design for the worldwide plasma-based accelerator facility, capable of delivering multi-GeV electron beams with high quality. This accelerator facility will be used for various user applications such as compact X-ray sources for medical imaging and high-energy physics detector tests. EuPRAXIA explores different approaches to plasma acceleration techniques. Laser-driven plasma wakefield acceleration with external injection of an RF-generated electron beam is one of the basic research directions of EuPRAXIA. We present studies of electron beam acceleration to GeV energies by a two-stage laser wakefield acceleration with external injection from an RF accelerator. Electron beam injection, acceleration and extraction from the plasma, using particle-in-cell simulations, are investigated.

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TUPML042

Accurate Modeling of the Hose Instability in Plasma Based Accelerators

electron, damping, simulation, wakefield

1638

T.J. Mehrling, C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
LBNL, Berkeley, USA

Funding: US Department of Energy Contract No. DE-AC02-05CH11231
The hose instability is a long standing challenge for plasma-based accelerators. It is seeded by initial transverse asymmetries of the beam or plasma phase space distributions. The beam centroid displacement is thereby amplified during the propagation in the plasma, which can lead to an unstable acceleration process. A witness beam can itself cause hosing and/or may be affected by the hosing of the drive beam. The accurate study of hosing including a witness beam is of utmost importance to facilitate stable plasma-based accelerators. In this contribution, we discuss novel methods for the mitigation of hosing and present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability of drive and witness beam pair in the nonlinear blowout regime. This work enables more precise and comprehensive studies of hosing and hence, for the potential stabilization of future compact plasma-based accelerators.

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TUPML046

Characterization of Self-Modulated Electron Bunches in an Argon Plasma

electron, experiment, solenoid, focusing

1645

M. Groß, P. Boonpornprasert, Y. Chen, J. Engel, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, R. Niemczyk, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
DESY Zeuthen, Zeuthen, Germany
R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
CFEL, Hamburg, Germany
F.J. Grüner, A. Martinez de la Ossa
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
T.J. Mehrling, C.B. Schroeder
LBNL, Berkeley, USA
I. Will
MBI, Berlin, Germany

The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect* the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 10¹³ cm^-3 to 1015 cm^-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing.
* M. Gross et al., "Observation of the self-modulation instabil-ity via time-resolved measurements", accepted for publication at Phys. Rev. Lett.

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TUPML047

Optimisation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ

wakefield, acceleration, laser, electron

1648

G. Loisch, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, M. Krasilnikov, O. Lishilin, A. Oppelt, Y. Renier, F. Stephan
DESY Zeuthen, Zeuthen, Germany
R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
CFEL, Hamburg, Germany
F.J. Grüner, A. Martinez de la Ossa
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The transformer ratio, the ratio between maximum accelerating field and maximum decelerating field in the driving bunch of a plasma wakefield accelerator (PWFA), is one of the key aspects of this acceleration scheme. It not only defines the maximum possible energy gain of the PWFA but it is also connected to the maximum percentage of energy that can be extracted from the driver, which is a limiting factor for the efficiency of the accelerator. Since in linear wakefield theory a transformer ratio of 2 cannot be exceeded with symmetrical drive bunches, any ratio above 2 is considered high. After the first demonstration of high transformer ratio acceleration in a plasma wakefield at PITZ, the photoinjector test facility at DESY, Zeuthen site, limiting aspects of the transformer ratio are under investigation. This includes e.g. the occurrence of bunch instabilities, like the transverse two stream instability, or deviations of the experimentally achieved bunch shapes from the ideal.

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TUPML049

Comparison of Fourier Signal and Error Analysis Techniques for Identifying the Self-Modulation Frequency of a Proton Bunch

proton, wakefield, electron, experiment

1651

S.J. Gessner
CERN, Geneva, Switzerland

The AWAKE experiment uses an ultra-high energy proton beam to create large amplitude wakefields for accelerating electrons in plasma. The proton beam is much longer than the plasma wavelength, and must be formed into small, sub- wavelength sized beamlets before it can effectively drive the wake. These beamlets are referred to as micro-bunches and are formed by the plasma self-modulation instability. An im- portant aspect of AWAKE is to measure the depth, frequency, and stability of the modulation, as this provides critical in- formation for establishing the presence of a high-amplitude wakefield driven by a self-modulation proton bunch. This paper discusses Fourier Analysis techniques for measuring the modulation frequency and compares error estimation techniques that work for both small and large datasets.
On behalf of the AWAKE Collaboration.

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TUPML051

Studies of Collision and Compression of Pulsed Plasmas Generated by Coaxial Accelerators

electron, experiment, ion-source, simulation

1653

T. Manegold, C. Benzing, M. Iberler, J. Jacoby, P. Mahmoodi Tavana, A. Müller-Münster, B. Podßus
IAP, Frankfurt am Main, Germany

This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 10¹⁵cm^-3. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 10¹⁸cm^-3.

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TUPML059

Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator

laser, beam-loading, simulation, electron

1670

X. Li, P.A.P. Nghiem
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France

GeV-scale laser-plasma accelerating modules can be integrated into a multi-staged plasma linac for driving compact X-ray light sources or future colliders. Such a plasma module, operating in the quasi-linear regime, has been designed for the 5 GeV laser plasma acceleration stage (LPAS) of the EuPRAXIA project. Although it can be employed to optimize the total energy spread, the beam loading effect introduces an non-negligible slice energy spread to the beam. In this paper, we study the slice energy spread from linear theory, establishing a relationship between it and the laser-plasma parameters. To reduce the slice energy spread, simulations have been carried out for various plasma densities and laser strengths. The results will be discussed and compared with the theory.

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TUPML066

Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices

simulation, emittance, scattering, cavity

1696

P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA
J.S. Ellison
IIT, Chicago, Illinois, USA

Funding: Work supported by the Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.

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TUPML070

Laser Ablation Plasma with Solenoid Field Confinement

laser, solenoid, target, ion-source

1706

G.C. Wang, Q. Jin, L.T. Sun, J. Zhang, X.Z. Zhang, H.W. Zhao, H. Zhao
IMP/CAS, Lanzhou, People's Republic of China

Funding: This work is supported by National Natural Science Foundation of China (Grant Nos. 11722547, 11605263 and 11505257) and West Light Foundation of The Chi-nese Academy of Sciences (Grant Nos. 29Y637020)
A Laser Ion Source (LIS) can produce high charge state and high intensity ion beams (~emA), especially refracto-ry metallic ion beams, which makes it a promising candi-date as an ion source for heavy ion cancer therapy facili-ties and future accelerator complexes, where pulsed high intensity and high charged heavy ion beams are required. However, it is difficult for LIS to obtain a long pulse width while ensuring high current intensity, thus limiting the application of LIS. To solve the conflict, magnetic fields are proposed to confine the expansion of the laser produced plasma. With a solenoid along the normal direc-tion to the target surface, the lateral adiabatic expansion of the laser ablation plasma is suppressed which extends the pulse width of the ion beam effectively.

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TUPML079

A Start to End Simulation of the Laser Plasma Wakefield Acceleration Experiment at ESCULAP

electron, laser, acceleration, wakefield

1731

K. Wang, C. Bruni, K. Cassou, V. Chaumat, N. Delerue, D. Douillet, S. Jenzer, V. Kubytskyi, P. Lepercq, H. Purwar
LAL, Orsay, France
E. Baynard, M. Pittman
CLUPS, Orsay, France
J. Demailly, O. Guilbaud, S. Kazamias, B. Lucas, G. Maynard, O. Neveu, D. Ros
CNRS LPGP Univ Paris Sud, Orsay, France
D. Garzella
CEA, Gif-sur-Yvette, France
R. Prazeres
CLIO/ELISE/LCP, Orsay, France

We present a start to end (s2e) simulation of the Laserplasma Wake Field Accelerator (LPWA) foreseen as the ESCULAP project. We use a photo injector to produce a 5 MeV 10 pC electron bunch with a duration of 1 ps RMS, it is boosted to 10 MeV by a S-band cavity and then compressed to 74 fs RMS (30 fs FWHM) by a magnetic compression chicane (dogleg). After the dogleg, a quadrupole doublet and a triplet are utilized to match the Twiss parameters before injecting into the subsequent plasma wakefield. A 40 TW laser is used to excite plasma wakefield in the 10 cm plasma cell. An optimized configuration has been determined yielding at the plasma exit an electron beam at 180 MeV with energy spread of 4.2%, an angular divergence of 0.6 mrad and a duration of 4 fs.

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WEPAF026

Beam Induced Fluorescence Measurements of 100 keV Deuterons in LIPAc Accelerator

electron, injection, detector, emittance

1877

R. Varela, A. Guirao, L.M. Martínez, J. Mollá, I. Podadera
CIEMAT, Madrid, Spain
T. Akagi, R. Ichimiya, Y. Ikeda, M. Sugimoto
QST, Aomori, Japan
B. Bolzon, N. Chauvin
CEA/IRFU, Gif-sur-Yvette, France
P. Cara
Fusion for Energy, Garching, Germany
H. Dzitko
F4E, Germany
J. Knaster
IFMIF/EVEDA, Rokkasho, Japan

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project FIS2013-40860-R
The LIPAc accelerator will be a linear CW deuteron accelerator capable of delivering a 9 MeV, 125 mA beam which aims to validate the technology that will be used in the future high power accelerator-driven neutron source, IFMIF. In summer 2017 a campaign of measurements was done during the injector commissioning, in which a Fluorescence Profile Monitor based on an Intensified CID camera (ICID) was used to measure the beam transverse profile at the extraction of the ion source. In this contribution we review the design of the ICID, its performance and discuss the measurements carried out. The performance of ICID monitors for its use in future accelerators will be assessed.

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WEPAF057

Electron Beam Diagnostics Concept for the ELI LUX Project

electron, diagnostics, laser, undulator

1954

K.O. Kruchinin, D. Kocon, A.Y. Molodozhentsev, L. Pribyl
ELI-BEAMS, Prague, Czech Republic
A. Lyapin
JAI, Egham, Surrey, United Kingdom

Nowadays the popularity of Laser Wakefield Accelerators (LWFA) is increasingly growing. Although the quality of the beams produced by LWFA is still lower than provided by conventional accelerators, they have great potential to be considered as a new basis for future FELs and even colliders. Laser Undulator X-ray (LUX) source is being commissioned at ELI-beamlines in Czech Republic. The goal of this machine is to provide photon beam in so called "water window" wavelength region for user experiments. Possible upgrade of the facility towards the LWFA based FEL is also considered. The electron beam diagnostics is absolutely crucial for achieving the aim of LUX. Specific properties of the beam produced by current LWFA, such as low charge, poor beam stability, big beam divergence and energy spread, require rethinking and adaptation of the conventional diagnostic tools and, in some cases, development of new ones. Ideally, they have to be compact, stable, non-invasive and allow measurements in single-shot mode. In this report we will present an overview and design considerations for the LUX electron beam main diagnostics. We will also discuss the hardware status and future plans.

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WEPAF070

Commissioning of Beam Instrumentation at the CERN AWAKE Facility After Integration of the Electron Beam Line

electron, proton, laser, experiment

1993

I. Gorgisyan, C. Bracco, S. Burger, S. Döbert, S.J. Gessner, E. Gschwendtner, L.K. Jensen, S. Jensen, S. Mazzoni, D. Medina, K. Pepitone, L. Søby, F.M. Velotti, M. Wendt
CERN, Geneva, Switzerland
M. Cascella, S. Jolly, F. Keeble, M. Wing
UCL, London, United Kingdom
V.A. Verzilov
TRIUMF, Vancouver, Canada

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a project at CERN aiming to accelerate an electron bunch in a plasma wakefield driven by a proton bunch*. The plasma is induced in a 10 m long Rubidium vapour cell using a pulsed Ti:Sapphire laser, with the wakefield formed by a proton bunch from the CERN SPS. A 16 MeV electron bunch is simultaneously injected into the plasma cell to be accelerated by the wakefield to energies in GeV range over this short distance. After successful runs with the proton and laser beams, the electron beam line was installed and commissioned at the end of 2017 to produce and inject a suitable electron bunch into the plasma cell. To achieve the goals of the experiment, it is important to have reliable beam instrumentation measuring the various parameters of the proton, electron and laser beams such as transverse position, transverse profile as well as temporal synchronization. This contribution presents the status of the beam instrumentation in AWAKE, including the new instruments incorporated into the system for measurements with the electron beam line, and reports on the performance achieved during the AWAKE runs in 2017.
* Gschwendtner E., et al. "AWAKE, the Advanced Proton Driven Plasma Wakefield Experiment at CERN", NIM A 829 (2016)76-82

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WEPAF074

Non-invasive Beam Diagnostics with Cherenkov Diffraction Radiation

photon, radiation, detector, electron

2005

T. Lefèvre, M. Bergamaschi, O.R. Jones, R. Kieffer, S. Mazzoni
CERN, Geneva, Switzerland
L.Y. Bartnik, M.G. Billing, Y.B.P. Bordlemay Padilla, J.V. Conway, M.J. Forster, J.P. Shanks, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Bergamaschi, P. Karataev
Royal Holloway, University of London, Surrey, United Kingdom
V.V. Bleko, A.S. Konkov, J.S. Markova, A. Potylitsyn
TPU, Tomsk, Russia
L. Bobb
DLS, Oxfordshire, United Kingdom
K. Lekomtsev
JAI, Egham, Surrey, United Kingdom

Based on recent measurements of incoherent Cherenkov Diffraction Radiation (ChDR) performed on the Cornell Electron Storage Ring, we present here a concept for the centering of charged particle beams when passing close to dielectric material. This would find applications as beam instrumentation in dielectric capillary tubes, typically used in novel accelerating technologies, as well as in collimators using bent crystals for high-energy, high-intensity hadron beams, such as the Large Hadron Collid-er or Future Circular Collider. As a charged particle beam travels at a distance of a few mm or less from the surface of a dielectric material, incoherent ChDR is produced inside the dielectric. The photons are emitted at a large and well-defined angle that allows their detection with a limited contribution of background light. A set of ChDR detectors distributed around a dielectric would enable both the beam position and tilt angle to be measured with a good resolution.

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WEPAG002

Tunable Q-Factor Gas-Filled RF Cavity

cavity, coupling, hadron, simulation

2064

M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, K. Yonehara, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.

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WEPAK001

Intense Neutrino Source Front End Beam Diagnostics System R&D

cavity, detector, target, hadron

2077

K. Yonehara, M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
We overview the front end beam diagnostic system R&D to prepare operation of a multi-MW proton beam for intensity frontier Neutrino experiments. One of critical issues is shorter life time of a detector with higher beam intensity due to radiation damage. We show a possible improvement of the existing ion chamber based detector, and a study of a conceptually new radiation-robust detector which is based on a gas-filled RF resonator.

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WEPAL065

Development of a Gas Sheet Beam Profile Monitor for IOTA

simulation, detector, space-charge, proton

2326

S. Szustkowski, B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
D.J. Crawford
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
A nitrogen gas sheet will measure the two dimensional transverse profile of the 2.5 MeV proton beam in IOTA. The beam lifetime is limited by the interaction with the gas, thus a minimally invasive instrument is required. To produce a gas sheet with the desired density and thickness, various nozzle types are being investigated, including rectangular capillary tubes for gas injection and skimmers for final shaping of the gas. It is essential to meet vacuum requirements in the interaction chamber while maintaining the precise thickness and density of the gas, without significantly affecting the beam lifetime. The current design of a gas sheet beam profile monitor and present status will be discussed.

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WEPMF061

High Gradient Pulsed Quadrupoles for Novel Accelerators and Space Charge Limited Beam Transport

quadrupole, focusing, electron, wakefield

2505

C. Tenholt
CERN, Geneva, Switzerland
G. Loisch, F. Stephan
DESY Zeuthen, Zeuthen, Germany
B. Marchetti
DESY, Hamburg, Germany

Novel acceleration schemes like plasma wake-field based accelerators demand for high gradient focusing elements to match the Twiss parameters in the plasma to the transport lattice of the conventional accelerator beamlines, with typically much higher beta-functions. There are multiple candidates for achieving high gradient focusing fields, each one having certain drawbacks. Permanent magnets are limited in tunability, plasma lenses might degrade the transverse beam quality significantly and conventional magnets cannot reach very high gradients and often cannot be placed in direct proximity of the plasma accelerator because of their size. In this paper we present design considerations and simulations on compact, high gradient, pulsed quadrupoles, that could be used e.g. for final focusing of space charge dominated bunches into a LWFA (Laser Wake-Field Accelerator) at SINBAD or other facilities with similar demands. The target design gradient is 200 T/m at a physical aperture on the order of 10 mm.

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WEPMK012

Update on Plasma Processing R&D for LCLS-II

cavity, HOM, experiment, SRF

2656

P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans, S.-H. Kim, K.E. Tippey
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.

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WEPML038

Plasma Window as a Pressure Valve for FAIR

cathode, experiment, electron, vacuum

2776

B. F. Bohlender, M. Iberler, J. Jacoby
IAP, Frankfurt am Main, Germany
A. Michel
Goethe Universität Frankfurt, Frankfurt am Main, Germany

Funding: Funded by BMBF, Ref. No: 05P15 RFRBA and HIC for FAIR
This contribution shows the progress in the development of a plasma window at the institute for applied physics at Goethe University Frankfurt. A plasma window* is a membrane free transition between two regions of different pressure, enabling beam transmission from a rough vacuum area (~1 mbar) to a higher pressure (up to 1 bar) region on short length scales. In comparison to differential pumping stages a length reduction by a factor of up to 100 is achievable, while the absence of a solid membrane yields prolonged operation time. The sealing effect is based on the high temperature arc discharge sustained in a cooled copper channel between the pressure regimes. Due to a bulk temperature around 10,000K** the viscosity of the gas is dramatically increased, leading to a slower gas flow, enabling a higher pressure gradient. This contribution will present first results regarding the pressure gradient in dependence of the discharge current and the aperture. Until now, a pressure factor around 100 has been established for well over 50 min. This contribution goes along with the one from Mr. A. Michel, he focuses on the spectroscopic analysis of the arc plasma.
*A. Hershcovitch, J. Appl. Phys., AIP Publishing (1995) 78, 5283
**Y.E. Krasik et al., "Plasma Window Characterization", J. Appl. Phys., AIP Publishing (2007) 101, 053305.

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THPAF005

Simulations of Modulator for Coherent Electron Cooling

electron, simulation, bunching, quadrupole

2953

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Highly resolved numerical simulations have been performed using the code SPACE for the modulator, the first section of the Coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Simulation results have been benchmarked with analytical solution using uniform electron beam with realistic thermal velocities. Electron bunches with Gaussian distribution and quadrupole field with realistic settings have been applied in the simulations to predict the modulation process and final bunching factors induced by ions with reference and off-reference energies in the CeC experiment at BNL RHIC.

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THPAF032

Simulation Study of an RF Injector for the LWFA Configuration at EuPRAXIA

linac, injection, emittance, simulation

3025

J. Zhu, R.W. Aßmann, A. Ferran Pousa, B. Marchetti, P.A. Walker
DESY, Hamburg, Germany

The Horizon 2020 Project EuPRAXIA (EuropeanPlasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with multi-GeV electron beams using a plasma accelerator. LWFA with external injection from an RF accelerator is one of the most promising configurations. In order to achieve the goal parameters for the 5 GeV, 30 pC electron beam at the entrance of the undulator, a high-quality electron beam with bunch length of less than 10 fs (FWHM) and matched beta functions (~1 mm) at the plasma entrance is required. In addition, from the compactness point of view, the injection energy is desired to be as low as possible. A hybrid compression scheme is considered in this paper and a detailed start-to-end simulation is presented.

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THPAK043

Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures

GPU, simulation, kicker, HOM

3309

Zh.C. Liu
IHEP, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.

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THPAK083

An s-Based Symplectic Spectral Space Charge Algorithm

space-charge, optics, simulation, proton

3425

N.M. Cook, D.T. Abell, D.L. Bruhwiler, J.P. Edelen, C.C. Hall, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340.
Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab.

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THPAK094

High Acceptance Beamline for the Capture of a Laser Wakefield Accelerated Beam

quadrupole, focusing, permanent-magnet, laser

3456

B.D. Muratori, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
K.A. Dewhurst
University of Manchester, Manchester, United Kingdom
K.A. Dewhurst, J.K. Jones, H.L. Owen
Cockcroft Institute, Warrington, Cheshire, United Kingdom
H.L. Owen
UMAN, Manchester, United Kingdom

Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.

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THPAK107

Space-Charge Hamiltonian with a Space Coordinate as Independent Variable

space-charge, TRIUMF, vacuum, synchrotron

3484

T. Planche, P. M. Jung, S.D. Rädel
TRIUMF, Vancouver, Canada

We present a version of the Low Lagrangian tailored to treat space-charge effects in particle accelerators: the Lagrangian is relativistic and uses a space coordinate as the independent variable. From this Lagrangian we obtain the corresponding Hamiltonian. From the Hamiltonian we obtain equations of motion for the 8 canonical variables, which can be plugged into a symplectic numerical integrator. We will finally discuss the possibility of numerically solving this problem using an explicit symplectic integrator.

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THPAK121

Accelerator Optimization through LIV. DAT

proton, radiation, experiment, wakefield

3526

C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: LIV. DAT is supported by the STFC under contract ST/P006752/1.
The Liverpool Big Data Science (LIV. DAT) Center for Doctoral Training (CDT) is a hub for training students in managing, analysing and interpreting large, complex datasets and high rates of data flow. LIV. DAT offers a unique training approach addressing some of the biggest challenges in data intensive science to tackle a growing skills gap. It currently provides training to a cohort of almost 20 PhD students. Their research projects address R&D challenges in astronomy, nuclear, particle and accelerator physics. This contributions presents initial research results from modeling studies of the physics and biology of proton beam therapy using a Monte Carlo approach, as well as plasma-beam interaction in the cases of AWAKE and EuPRAXIA.

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THPAK136

Wide-Ranging Genetic Research of Matching Line Design for Plasma Accelerated Beams with GIOTTO

emittance, electron, target, FEL

3561

M. Rossetti Conti
Universita' degli Studi di Milano & INFN, Milano, Italy
A. Bacci, A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
A. Giribono, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy

GIOTTO is a code based on a Genetic Algorithm, being used in the field of particles accelerators for some years*-***. Its main use concerns beam-dynamics optimizations for low energy linacs, or injectors, where the beam space-charge plays an important role on its dynamics. Typical optimizations regard the Velocity Bunching technique or, more generally, the emittance and energy spread minimization. Recent improvements in GIOTTO, here discussed, have added the important capability to solve problems with a wide research domain, making GIOTTO able to design a beam Transfer Line (TL) from scratch****. The code, taking as input the TL length and the optics elements, can define the correct lattice of the line that transports and matches the beam from the linac to the undulators of an FEL, finding the right gradients, positions and dimensions for the optics elements by exploring the parameters values in selected ranges. Further, the introduction of Twiss parameters into the fitness function makes GIOTTO a powerful tool in the design of highly different beam lines. Lastly, a new routine for the statistical analysis of parameters jitters effects on the beam is under development.
*Bacci et al, NIM-B, 263, 488 (2007)
**Bacci et al, presented at PAC'07, THPAN031
***Bacci et al, presented at IPAC'16, WEPOY039
****Rossetti Conti et al, NIM-A (2018, in press)

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THPAL065

Improving the Work Function of Nitrogen-Doped Niobium Surfaces for SRF Cavities by Plasma Processing

cavity, niobium, SRF, accelerating-gradient

3802

K.E. Tippey, R. Afanador, M. Doleans, S.-H. Kim, J.D. Mammosser, C.J. McMahan
ORNL, Oak Ridge, Tennessee, USA
M. Martinello
Fermilab, Batavia, Illinois, USA

Funding: DOE research grant FWP-ERKCSA2; DOE contract DE-AC05-00OR22725
Work function and surface chemistries of SiC-polished, electropolished, and nitrogen-doped niobium coupons were analyzed before and after plasma processing using a neon-oxygen gas mixture. These studies represent an initial enquiry into the feasibility of applying the plasma processing technique designed at ORNL for the Spallation Neutron Source (SNS) to the nitrogen-doped Nb cavities for the Coherent Light Source II (LCLS-II). Work function of all measured samples was increased after plasma processing, which indicates the strong potential of the plasma processing technique as a tool for increasing the accelerating gradient of nitrogen-doped cavities.

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THPAL069

Simulation of a 10 mm Diameter Cascaded Plasma Window

cathode, simulation, vacuum, experiment

3812

P.P. Gan, S. Huang, Y.R. Lu, S.Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.

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THPAL083

A Test Facility for Developments in Ion Source Plasma Power Supplies

power-supply, controls, ion-source, electronics

3845

R.E. Abel, D.C. Faircloth, S.R. Lawrie, J.H. Macgregor, M. Perkins
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

A new test facility is being designed and constructed at the ISIS spallation neutron source, Rutherford Appleton Laboratory, for the purpose of developing and experimenting with new plasma power supply topologies and modes of operation. The test facility will allow better control of power supply parameters such as discharge pulse current and plasma ignition voltage along with the possibility for closed loop feedback control. The design and technical construction details are presented with an overview of the plasma power supply developments.

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THPAL095

Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory

cathode, electron, gun, laser

3865

A.N. Hannah, J.A. Conlon, L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
V. R. Dhanak
The University of Liverpool, Liverpool, United Kingdom
L.B. Jones, B.L. Militsyn
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Lederer
DESY Zeuthen, Zeuthen, Germany
S. Lederer
DESY, Hamburg, Germany

The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10^-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.

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THPAL102

Design a High Power Pulse Transformer for C-band Klystron Modulator

flattop, klystron, high-voltage, FEL

3875

Y.F. Liu, Z.H. Chen, M. Gu, Y. Wu, Q. Yuan, X.X. Zhou
SINAP, Shanghai, People's Republic of China

Shanghai soft X-ray Free Electron Lasers (SXFEL) first uses C band accelerator structure to accelerate electrons at SINAP. SXFEL is an X-ray free electron laser facility, which requests very stable amplitude stability and very tight tolerances of phase jitter. 50MW C-band klystron and 110MW modulator is used to provide power supply for accelerator structure. Typical specifications of the modulator are peak beam voltage 350KV, peak beam current 320A, 10Hz repetition rate, 3us flat-top pulse width. In order to meet these demands, we developed a reliable and stable high power pulse transformer. In this paper, the analysis and design of high power pulse transformer for C band klystron modulator are presented. The methods of shortening rise time, diminishing droop and diminishing flat top oscillation are highlighted. Detailed design, simulation and relevant experimental results are given. The relevant experiments show that this pulse transformer can meet the requirement of 50MW C band klystron.

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THPMF014

First Experiments at the CLEAR User Facility

electron, experiment, radiation, operation

4066

R. Corsini, A. Curcio, S. Curt, S. Döbert, W. Farabolini, D. Gamba, R. Garcia Alia, T. Lefèvre, G. McMonagle, P.K. Skowroński, M. Tali, F. Tecker
CERN, Geneva, Switzerland
E. Adli, C.A. Lindstrøm, K.N. Sjobak
University of Oslo, Oslo, Norway
R.M. Jones, A. Lagzda
UMAN, Manchester, United Kingdom

The new "CERN Linear Electron Accelerator for Research" (CLEAR) facility at CERN started its operation in fall 2017. CLEAR results from the conversion of the CALIFES beam line of the former CLIC Test Facility (CTF3) into a new testbed for general accelerator R&D and component studies for existing and possible future accelerator applications. CLEAR can provide a stable and reliable electron beam from 60 to 220 MeV in single or multi bunch configuration at 1.5 GHz. The experimental program includes studies for high gradient acceleration methods, e.g. for CLIC X-band and plasma technology, prototyping and validation of accelerator components, e.g. for the HL-LHC upgrade, and irradiation test capabilities for characterization of electronic components and for medical applications. An overview of the facility capabilities and a summary of the latest results will be presented.

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THPMF086

Reliability Improvement on Wiggler Period Averaging Approximation

wiggler, FEL, simulation, laser

4281

K. Hwang, J. Qiang
LBNL, Berkeley, California, USA

Funding: US Department of Energy under Contract no. DEAC02-05CH11231
As the wiggler period averaging is subject to reliability issue, many efforts on FEL codes without such approximations are made at the cost of heavier computation loads. However, efforts toward increasing the reliability of such approximation are few. In this report, we present a new capability of IMPACT code suite based on such approximation with the addition of perturbative corrections to wiggler period averaging error.

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THPMK063

Photocathode Preparation and Characteristics of the Electron Source for the VELA/CLARA Facility

cathode, laser, electron, operation

4442

T.C.Q. Noakes, D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, M.D. Roper, E.W. Snedden, R. Valizadeh, D.A. Walsh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The VELA and CLARA front end accelerators at Daresbury are test facilities with a focus on FEL research and industrial applications of electron beams. Recently the CLARA injector has been commissioned with acceleration of beam to 50 MeV. For several years a normal conducting 2.5 cell S-band cavity RF gun operated at up to 80 MV/m has been used as the electron source for both VELA and CLARA. For further beam acceleration an S-band travelling wave 2m long cavity has been used. The gun has used several different copper cathodes throughout its operational life, employing different preparation techniques. Oxygen plasma treatment is a well-known procedure for removing hydrocarbon contamination from surfaces whereas Argon plasma treatment also removes contaminants and typically leaves a thinner oxide at the surface. In this study we compare dark current (from field emission), as measured directly after the gun, for these alternate surface preparations and also present results from post-use electron microscopy analysis of the photocathodes. Electromagnetic simulations are used to help explain the results.

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THPMK076

Longitudinal Shaping for Beam-Driven Plasma Wakefield Accelerators

electron, linac, FEL, simulation

4477

Z. Wang, K.Q. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
S. Huang, W. Lu
TUB, Beijing, People's Republic of China

The generation of high quality driven electron beam (high peak current and small beam size) is quite important for the beam-driven plasma accelerator. Besides, a linearly ramped, more exactly, the triangular current distribution is more suitable. In this paper, by adjusting the phase and the amplitude of the harmonic linearizer, the linear ramped current distribution electron beam is generated by the FEL linac. The CSR introduced emittance growth and the jitters of the electron are researched. The electron beam generated by the ramped driven beam in the plasma is researched as well.

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THPML002

Emittance Preservation in Plasma-Based Accelerators with Ion Motion

emittance, wakefield, background, ECR

4654

C. Benedetti, E. Esarey, W. Leemans, T.J. Mehrling, C.B. Schroeder
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. DOE under Contract No. DE-AC02-05CH11231.
In a plasma-accelerator-based linear collider, the density of matched, low-emittance, high-energy particle bunches required for collider applications can be orders of magnitude above the background ion density, leading to ion motion, perturbation of the focusing fields, and, hence, to beam emittance growth. By analyzing the response of the background ions to an ultrahigh density beam, analytical expressions, valid for non-relativistic ion motion, are obtained for the perturbed focusing wakefield. Initial beam distributions are derived that are equilibrium solutions, which require head-to-tail bunch shaping, enabling emittance preservation with ion motion.

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THPML009

Polarized Deuteron Negative Ion Source for Nuclear Physics Applications

polarization, laser, ion-source, electron

4665

V.G. Dudnikov, M.A. Cummings, R.P. Johnson
Muons, Inc, Illinois, USA
A.V. Sy
JLab, Newport News, Virginia, USA

The proposed U.S. Electron-Ion Collider (EIC) provides a unique tool to explore the next frontier in Quantum Chromodynamics, the dependence of hadron structure on the dynamics of gluons and sea quarks. Polarized beams are essential to these studies; understanding of the hadron structure cannot be achieved without knowledge of the spin. The existing EIC concepts utilize both polarized electrons and polarized protons/light ion species to probe the sea quark and gluon distributions. Polarized deuterons provide an especially unique system for study by essentially providing a combination of quark and nuclear physics. We note that there are currently no operational polarized deuteron beam sources in the United States. This polarized deuteron source can serve as a polarized deuteron injector for a future EIC, with additional applications in polarimetry and polarized gas targets for experiments at CEBAF or RHIC and would be very useful for our future facilities.

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THPML018

Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses

laser, electron, focusing, target

4690

C.-Y. Hsieh, S.-H. Chen
NCU, Chung Li, Taiwan
M.W. Lin
National Tsing-Hua University (NTHU), Hsinchu, Taiwan

Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3.
Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target*. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems**. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly.
* A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015).
** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016).

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THPML031

Collective Acceleration of Laser Plasma in Non-stationary and Non-uniform Magnetic Field

laser, acceleration, target, experiment

4716

A.A. Isaev, C.I. Kozlovskij, E.D. Vovchenko
MEPhI, Moscow, Russia

This paper presents the new experimental results concerning acceleration of deuterium ions extracted from laser plasma in the rapid-growing nonuniform magnetic field in order to initiate the nuclear reactions D(d, n)3He and Т (d,n)4He. In order to obtain plasma a laser that generates in Q-switched mode the pulses of infrared radiation (λ = 1.06 μm) with the energy W ≤ 0.85 J and duration of ≈10 ns. In the present study, the velocity of a bunch of a laser plasma at a magnetic field induction rate of 3-10⁸ T/s was experimentally measured, and angular distributions of accelerated particle fluxes were measured in the range from 0 to 30 degrees. The maximum and mean ion velocities were determined by the time-of-flight technique. The proposed system allows the generation of neutrons, including possibly thermonuclear ones, on counterflows using two similar magnetic accelerators located coaxially, facing each other. In this case the problem related to degradation of solid neutron-generating targets is resolved. There also occurs a possibility of fast accumulated running time of packed solid targets at using of deuteron-tritium laser targets.

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THPML033

Towards a Free Electron Laser Using Laser Plasma Acceleration

electron, laser, free-electron-laser, FEL

4723

A. Loulergue, T. André, I.A. Andriyash, C. Benabderrahmane, P. Berteaud, F. Blache, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Chapuis, M.-E. Couprie, D. Dennetière, Y. Dietrich, J.P. Duval, M. El Ajjouri, T.K. El Ajjouri, A. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitegi, M. Labat, N. Leclercq, A. Lestrade, O. Marcouillé, F. Marteau, P. N'gotta, D. Oumbarek, F. Polack, P. Rommeluère, M. Sebdaoui, K.T. Tavakoli, M. Valléau, J. Vétéran, C. de Oliveira
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, C. Evain, E. Roussel, C. Szwaj
PhLAM/CERLA, Villeneuve d'Ascq, France
S. Corde, J. Gautier, J.-P. Goddet, G. Lambert, B. Mahieu, V. Malka, J.P. Rousseau, S. Sebban, K. Ta Phuoc, A. Tafzi, C. Thaury
LOA, Palaiseau, France
O. S. Kononenko
DESY, Hamburg, Germany
S. Smartzev
Weizmann Institute of Science, Physics, Rehovot, Israel

Since the laser invention, the advent of X-ray Free Electron Lasers (FEL) half a century later, opens new areas for matter investigation. In parallel, the spectacular development of laser plasma acceleration (LPA) with several GeV beam acceleration in an extremely short distance appears very promising. As a first step, the qualification of the LPA with a FEL application sets a first challenge. Still, energy spread and beam divergence do not meet the state-of-the-art performance of the conventional accelerators and have to be manipulated to fulfill the FEL requirement. We report here on the undulator spontaneous emission measured after a transport manipulation electron beam line, using variable permanent magnet quadrupoles of variable strength for emittance handing and a demixing chicane equipped with a slit for the energy spread. Strategies of control electron beam position and dispersion have been elaborated. The measured undulator radiation provides an insight on the electron beam properties.

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THPML042

Integrating the Lorentz Force Law for Highly-Relativistic Particle-in-Cell Simulations

laser, simulation, acceleration, radiation

4734

A.V. Higuera, J.R. Cary
Tech-X, Boulder, Colorado, USA
J.R. Cary
CIPS, Boulder, Colorado, USA

Funding: This work is supported by the DOE under Grants No. DE-SC0011617 and DE-SC0012444, and by DOE/NSF Grant No. DE-SC0012584
Integrating the Relativistic Lorentz Force Law for plasma simulations is an area of current research (*, **, ***). In particular, recent research indicates that interaction with highly-relativistic laser fields is particularly problematic for current integration techniques (****). Here is presented a special-purpose integrator yielding improved accuracy for highly-relativistic laser-particle interactions. This integrator has been implemented in the particle-in-cell code VSim, and the authors present an accuracy and performance comparison with several particle push methods.
* http://aip.scitation.org/doi/abs/10.1063/1.4979989
** https://arxiv.org/abs/1702.04486
*** https://arxiv.org/abs/1710.09164
**** http://aip.scitation.org/doi/abs/10.1063/1.4905523

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML042

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THPML043

Optimization of Dielectric Laser-Driven Accelerators

laser, electron, simulation, acceleration

4737

C.P. Welsch, M.G. Ibison, Y. Wei
The University of Liverpool, Liverpool, United Kingdom
M.G. Ibison, Y. Wei, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191.
Dielectric laser-driven accelerators (DLAs) utilizing large electric field from commercial laser system to accelerate particles with high gradients in the range of GV/m have the potential to realize a first particle accelerator ‘on a chip'. Dual-grating structures are one of the candidates for DLAs. They can be mass-produced using available nanofabrication techniques due to their simpler structural geometry compared to other types of DLAs. Apart from the results from optimization studies that indicate the best structures, this contribution also introduces two new schemes that can help further improve the accelerating efficiency in dual-grating structures. One is to introduce a Bragg reflector that can boost the accelerating field in the channel, the other applies pulse-front-tilt operation for a laser beam to help extend the interaction length.

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THPML051

Electron Acceleration by Plasma Wave in the Presence of a Transversely Propagated Laser with Magnetic Field

electron, laser, acceleration, wakefield

4749

M. Yadav, S. C. Sharma
DELTECH, New Delhi, India
D.N. Gupta, M. Kaur
University of Delhi, Delhi, India

It has been revealed that a relativistic plasma wave, having an extremely large electric field, may be utilized for the acceleration of plasma particles. The large accelerating field gradient driven by a plasma wave is the basic motivation behind the acceleration mechanism. Such a plasma wave can be excited by a single laser in the form wakefield in laser-plasma interactions. In this paper, we study the enhancement of electron acceleration by plasma wave in presence of a laser* propagated perpendicular to the propagation of the wake wave. Electrons trapped in the plasma wave are effectively accelerated by the additional field of the laser combined with wakefield. The additional resonance provided by the laser field contributes to the large energy gain of electrons during acceleration. The resonant enhancement of electron acceleration has been validated by single particle simulations**. The dependence of energy gain on laser intensity, laser spot size, initial electron energy, and electron trajectories have been investigated.
* G. D. Tsakiris, C. Gahn, and V. K. Tripathi, Phys. Plasmas 7, 3017 (2000)
** Maninder Kaur, and D. N. Gupta, IEEE, 45, p 2841 - 2847, (2017)

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THPML052

Excitation of Plasma Wave by Lasers Beating in a Collisional and Mild-Relativistic Plasma

laser, electron, damping, ECR

4752

M. Kaur, D.N. Gupta
University of Delhi, Delhi, India

Funding: Work supported by Department of Science and Technology (DST), Government of India.
Excitation of plasma wave by two lasers beating in a collisional dominated relativistic plasma is investigated. We study the energy exchange between a plasma wave and two co-propagating lasers in plasma including the effect of relativistic mass change and electron-ion collisions. Two lasers, having frequency difference equal to the plasma frequency, excite a plasma beat wave resonantly by the ponderomotive force, which obeys the energy and momentum conservation*. The relativistic effect and the electron-ion collision both contribute in energy exchange between the interacting waves in the beat-wave acceleration mechanism. Our study shows that the initial phase difference between interacting waves generates a phase mismatch between lasers and plasma wave, which alters the rate of amplitude variations of the interacting waves and, hence, affects the energy exchange between the interacting waves**. This study may be crucial to design a compact plasma accelerator in low-intensity regime***.
*T. Tajima, and J. Dawson, Phys. Rev.Lett. 43, 267(1979)
**D. N. Gupta, M. S. Hur, and H. Suk, J.Appl. Phys. 100, 103101 (2006)
***M. Kaur and D. N. Gupta, EuroPhysics letter 116, 35001 (2016).

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THPML118

The AWAKE Electron Spectrometer

proton, electron, background, radiation

4947

F. Keeble, M. Cascella, J. A. Chappell, L.C. Deacon, S. Jolly, M. Wing
UCL, London, United Kingdom
I. Gorgisyan, S. Mazzoni
CERN, Geneva, Switzerland
P.L. Penna, M. Quattri
ESO, Garching bei Muenchen, Germany

The AWAKE experiment at CERN aims to use a proton driven plasma wakefield to accelerate electrons from 10–20 MeV up to GeV energies in a 10 m plasma cell. We present the design of the magnetic spectrometer which will measure the electron energy distribution. Results from the calibration of the spectrometer's scintillator and optical system are presented, along with a study of the backgrounds generated by the 400 GeV SPS proton beam.

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